Understanding Color

Understanding

Color

Understanding

Color

K e n n e t h F . H o f f m a n n

In a Digital Workflow

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UnderstandingColor

Kenneth F. HoffmannDigital Imaging & Publishing Technology

National Technical Institute for the Deaf

Rochester Institute of Technology

1999

In a Digital Workflow

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Understanding Color in a Digital Workflow Kenneth F. Hoffmann page i

Table of ContentsTh

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Part One: Color from Design to Print . . . . . . . . . . . . . . . . . . . 1

1. Project planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43. Conventional prepress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54. Digital prepress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65. Digital file output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76. File to print options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87. Choosing a print process . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Part Two: How Do We See Color, Anyway . . . . . . . . . . . . . . . 10

1. The human eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112. The electromagnetic spectrum . . . . . . . . . . . . . . . . . . . . . . . 123. Absorption and reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . 144. Color perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155. The language of color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166. Color and emotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187. Emotional & physiological responses to color . . . . . . . . . . . 198. Physiological factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209. Temperature of light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2110. Why do we print in color? . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Part Three: Comparative Color Models . . . . . . . . . . . . . . . . . 25

1. Additive color: RGB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262. Subtractive color: CMYK . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273. Artist’s color wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284. Alternate artist’s color wheel and color triangles . . . . . . . . . 295. CIE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306. Munsell color: Hue Value Chroma . . . . . . . . . . . . . . . . . . . . 32

Part Four: What is Color Separation? . . . . . . . . . . . . . . . . . . 33

1. How do color scanners work? . . . . . . . . . . . . . . . . . . . . . . . . 342. How do digital cameras work? . . . . . . . . . . . . . . . . . . . . . . . 363. Analog to digital conversion . . . . . . . . . . . . . . . . . . . . . . . . . 374. Process color printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385. Steps to good color reproduction . . . . . . . . . . . . . . . . . . . . . 396. The function of ink and toner on paper . . . . . . . . . . . . . . . . 407. The halftone dot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418. Stochastic screening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 449. Dot gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4510. GCR and UCR Color Replacement . . . . . . . . . . . . . . . . . . . . . 46

Understanding Color in a Digital Workflow Kenneth F. Hoffmann page ii

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Part Five: Working With Digital Files . . . . . . . . . . . . . . . . . . 47

1. Bitmapped images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 482. Grayscale and color bitmapped images . . . . . . . . . . . . . . . . . 493. Bit depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504. Vector graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 515. Fonts are vector images . . . . . . . . . . . . . . . . . . . . . . . . . . . . 546. Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 557. Interpolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 568. Resolution rules for scanning . . . . . . . . . . . . . . . . . . . . . . . . 579. Output resolution, lpi, and gray levels . . . . . . . . . . . . . . . . . 5810. File types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5911. File types and sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6012. File Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Part Six: Using Color Within Applications . . . . . . . . . . . . . . . 63

1. Choosing color with a color picker . . . . . . . . . . . . . . . . . . . . 642. Process versus Solid Color . . . . . . . . . . . . . . . . . . . . . . . . . . 693. High-Fidelity Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714. Pantone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 725. Trumatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 756. Color Naming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Part Seven: Color Management . . . . . . . . . . . . . . . . . . . . . . . 78

1. Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 792. Need for Color Management . . . . . . . . . . . . . . . . . . . . . . . . . 813. Color Predictability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824. Tools for Color Management . . . . . . . . . . . . . . . . . . . . . . . . 835. Color Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 846. Device Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 857. Color Management Modules . . . . . . . . . . . . . . . . . . . . . . . . . 86

Part Eight: Digital Color Printing . . . . . . . . . . . . . . . . . . . . . 87

1. Xerography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 882. Steps in the xerogrphy process . . . . . . . . . . . . . . . . . . . . . . . 893. Ink-jet printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904. Digital Printing Market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 915. Defining Run Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 926. Variable Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 937. Print-On-Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 948. Competitive Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Part One:Color from Design to Print

Understanding Color in a Digital Workflow Kenneth F. Hoffmann page 1

Overview of Part OneTh

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Part One:

Color from Design to Print

Objectives: at the completion of this part, you will be able to:

1. Explain the major factors to be considered when planning a print project.

2. Explain how project variables may influence cost, design, substrate, printprocess, and binding.

3. Compare the steps required to print a job on a digital press and an offset press.

Printing is one of the few industriesin which customers take an activepart in manufacturing...Customersand printers work together through-out the process.

Mark Beach and Eric Kenly

How is a print job produced? What are the design and production considerations? What arethe steps needed to produce a color print job? What print process technology is best used?What decisions and compromises need to be made? In this part you will learn the comparethe steps needed to produce a print job by conventional and digital processes and understandthe decision-making processes involved.

Key words to learn in this part:

Turnaround time Substrate

Conventional prepress Digital prepress

Preflighting Trapping

Imposition Proofing

Raster Image Processor Workflow

Imagesetter Platesetter

Output device Digital printer

Computer-to-film Reverse engineering

Computer-to-plate Offset lithography

Computer-to-press Gravure

Analog Flexography

Part One: Color from Designto Print

1. Project planning and theimpact on design andproduction

2. Conventional prepressworkflow steps

3. Digital prepress work-flow steps

4. Comparison of digitalprinting and offset print-ing workflows

5. Factors in choosing aprinting process



Project PlanningTh

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Project Planning & Graphic Design“Quality is best achieved when expectations

and product or performance requirements are clearly defined in the planning stages.” (GRACoL)

Planning ahead influences both the quality and the cost of the final product. Projects should be reverse engineered to guarantee that the planned project can actually be produced to specifications with given resources.

Project Questions

GRACoL (General Requirements for Applications in CommercialOffset Lithography) from Graphic Communications Association(GCA) is a set of guidelines established to encourage communica-tion at all steps of the production process.

Following is a series of questions, loosely based on the GRACoLguidelines. Similar questions apply equally well when planning offset printing, digital printing, and digital media projects. Project planning may also include the distribution requirements.

❶ Cost: what is your budget for the project?

Be realistic and plan within your means. Make appropriatecompromises. Cost will impact everything from designeffort, quantity, colors, paper selection, size and layout,and printing method, to binding and finishing proceduresfor function and appearance enhancement.

❷ Audience: who is the intended user/viewer?

The audience will impact everything from product type,design, appearance, and font selection to distributionstrategies, product function and permanence.

❸ Turnaround time: when is the project needed?

The needed delivery time may impact choice of printingtechnology (e.g., digital vs. offset), print supplier, substrateavailability, binding and finishing methods. Is the projecttimeline measured in hours or days?

❹ Substrate: what is the project purpose?

The type of substrate is dependent on project function,intended permanence, finishing effects, bulk and weightlimitations, appearance, printing and binding spec.

Things to DoDevelop a set of jobspecifications includingsuch aspects as projectdescription, budget,quantity, audience, time-line, and the substrate.

Create a role playingscenario for customer,designer, print buyer, andprinter’s customer ser-vice representative.

As the virtual project isplanned, designed, andproduced, see how thespecification variablesimpact the project.

Remember, problemanalysis and problemsolving requires breakingthe big problem into aseries of small problems.



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❺ Colors: how many colors are needed? desired? afford-able?

While some products require special spot colors,process (CMYK) colors may be used to substitute forspot colors in all printing processes. Digital printingis most often either black only or process color(there are some highlight color digital print devices).

The choice of colors may impact cost, project time-lines, and printing method.

❻ Proofing: what proofing is expected? who need toevaluate the proofs? local or remote?

The type and frequency of proofs required for a givenproject can vary widely based on the different costsand quality levels expected of the project, as well asthe complexity and difficulty of the project.

Proofing can surely prevent costly errors but exces-sive proofing can unnecessarily add to turnaroundtime and overall project costs.

❼ What special finishing is required?

Some finishing procedures such as embossing, foilstamping, varnishing, and thermography may haveaesthetic value only. The cost vs. impact value shouldbe evaluated.

Some finishing procedures such as trimming, fold-ing, die cutting, coating may have product perfor-mance functions. Some finishing may be both func-tional and aesthetic in value.

❽ What binding method is required?

Product permanence, flexibility, function, user pref-erences, cost, and turnaround time may all impactthe choice of binding methods.

❾ Where will production steps be completed?

Production can be done at locations anywhere. Whatare the workflow, cost, quality, and time implicationswhen a project moves through several locations?

Print-then-distribute or distribute-then-print?

Planning

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WorkflowTh

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The Print Production Workflow SegmentsPre-Press

From design to production of the image carrier

Press

The process for transferring image to substrate

Post-Press

Final manufacturing processes: folding, conversion, binding, forming, die cutting, etc.

There is No "One" WorkflowWorkflow variables include:

• Planning/Scheduling

• Job specifications from design to finishing

• Quantity to be delivered

• Turnaround time for delivery

• Equipment capacities and capabilities

• Distribution strategies

• Personnel availability and capabilities

• Solutions to unforeseen problems

Reverse EngineeringPrint production is a manufacturing process. Like any manufacturing process, productionneeds to be carefully planned. Reverse engineering the print project means identifying theexact production needs and timelines required before the project gets started in the produc-tion sequence. Material specifications are determined. Specific press and post-press equip-ment is identified and reserved for the project. Project cost estimates depend on accurateplanning and scheduling.



Conventional PrepressTh

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Disappearing Procedures,

Forgotten VocabularyThese procedures and materials haveessentially disappeared, or are rapidlydisappearing from the prepress work-flow of many companies:

Airbrush retouching

Typesetting

Paste-up

Mechanical art

Press type

Diffusion transfer stats

Camera line negatives

Camera halftones

Contact screens

Screen tints

Camera separations

Wet dot-etching

Dry dot etching

Amberlith/rubylith masking

X-acto knife

Rubber cement

Waxers

Contacts and dupes

Spreads and Chokes

Construction stripping

Analog platemaking

Conventional PrepressConventional prepress is based on the need to buildindividual analog page images, convert the pageimages to film, and use the film to expose proofs andprinting plates. Timelines measured in hours and days.

These procedures are still being practiced in the print-ing industry today, but their use is already extinct inmost companies and rapidly declining in all segmentsof the printing and publishing marketplace.

With the advent of desktop publishing and the abilityto easily make digital pages, including complex imageand color specifications, conventional prepress crafts-manship is being replaced by computer skills.

Conventional prepress workflow:

Design developed and sketched

Type is set on phototypesetter

Pages are made on paste-ups

Line negatives made of pages

Halftone negatives made of photos

Color separation negatives made

Page negatives stripped onto flats

Proofs made from film flats

Plates made from film flats

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Digital PrepressTh

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New Procedures

New Tools

New VocabularyThe evolution of digital prepress hasdramatically changed the creative andproduction procedures, tools andvocabulary. A 15- to 20-year oldgraphic arts textbook would likelyhave no references to these items:

Adobe Photoshop

Adobe Illustrator

Adobe PageMaker

Adobe Acrobat

Adobe InDesign

QuarkXPress

Macromedia Freehand

KPT Bryce

Painter

Kai’s Power Tools

Plug-ins and XTensions

WACOM tablet, digital pen

PostScript, PDF,TIFF, JPEG

Lossy compression

Lossless compression

RAM

Internet

Raster Image Processor

Imagesetter

Computer-to-Plate

Digital PrepressWhen the term “desktop publishing” was first coined,many printers associated the process with lesser quali-ty, amateurish document files that would not producethe desired and expected results. Now, no printingbusiness can successfully compete and grow withoutdesktop prepress or digital prepress as now termed.

Digital prepress today is clearly superior than conven-tional prepress. Pages are produced faster, with a muchhigher quality level, and at less cost. Color is far easierto design into a project and far easier to produce.

Digital prepress enables those with computer skills andknowledge of quality criteria to replace traditional pre-press crafts. The mouse has replaced the X-acto knife.

Design options developed

Type created in word processing

Graphic images made on computer

Photos are scanned: b&w or color

Page layouts made on computer

Text & images combined on page

Pages are digitally proofed

Pages output to film /analog plates

Pages output to digital plates

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Digital File OutputTh

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Preflighting

The process of verifying that all graphic, page, and document files have been prepared follow-ing all design and production specifications prior to file output.

Trapping

The overlap of adjacent image edges to allow for a registration tolerance between color unitson the (non-digital) printing press. Trapping software is used to alter the digital image filesper specific production requirements. Trapping is a production, not a design, responsibility.Trapping can be performed by workstation application or RIP software.

Imposition

The positioning of page images on the press sheet to meet all press, finishing, and bindingrequirements. Imposition is a production, not a design, responsibility. Imposition can be per-formed by workstation application or RIP software.

RIP (raster image processor)

The RIP (raster image processor) is the computer for an output device that receives andinterprets the PostScript page description and drives the imaging mechanism in the outputdevice.

PostScript Output Device

Imagesetters are PostScript output devices which image films that are used in analogplatemaking workflows. A computer-to-plate platesetter makes plates off the press. A com-puter-to-press platemaking system images the plates on the press printing unit. A digitalprinter is a PostScript output device with a re-imageable image carrier.

Desktop Publishing

Workstations

OutputDevice

imagesetter

platesetter

printerRaster Image

Processor(RIP)

Server

network connectivityamong all devices



File to Print OptionsTh

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File to Print OptionsWhen a digital file is ready for offset or digital printing production, there are four optionswhich are commonly used in the industry today:

• Computer-to-digital printer - Pages are directly imaged on re-imageable surface andprinted with the xerographic process or variation. Printing can be either simplex orduplex and is immediately dry when printed.

• Computer-to-film (CTF) output - partially or fully imposed films are produced on animagesetter. Pin-register systems are frequently used to automate the registrationprocess and to eliminate any manual film mounting and registration procedures ona light table. Analog platemaking is required from the films.

• Computer-to-plate (CTP) output - fully imposed pages are produced directly ontothe plate by a platesetter. No films are needed or produced, Pin-register systems areused to automate the plate registration and plate mounting on the offset press.

• Computer-to-press (CTPr) output - pages are directly imaged onto plates alreadypositioned on the offset press cylinders. Laser imaging devices are incorporated inthe press unit. Usually, waterless offset printing technology is utilized. Also calleddirect imaging (DI) offset and hybrid digital/offset.

Comparative File-to-Print Workflows and Timelines

DigitalFile

Preparation

Digital FilePreparation

andProofing

Digital FilePreparation

andProofing

Sheetfed OffsetLithography Printing

Sheetfed OffsetLithography Printing

DirectImaging

OffsetPrinting

DigitalPrinting

Computer-to-Film (CTF)Analog Proofs and Plates

Digital ProofsComputer-to-Plate (CTP)

Digital proofing and computer-to-plateworkflow can save many hours comparedto CTF, analog proofing and analogplatemaking workflow.

Sheetfed offset and direct-imaging offsetprinting may require significant ink dryingtime between sides and prior to finishingand binding procedures.

Digital printing has no delay for platemak-ing; toners are fused and dry immediately;duplex printing capability is the norm.Production times measured in minutes andhours, rather than hours and days.



Choosing a Print ProcessTh

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Choosing a Printing ProcessThe primary printing processes today include:

• Offset Lithography - printing from a flat plate, usually onto paper substrate, but canprint on some plastic films and even metal; sheetfed and web press configurations;single and two-sided press configurations; web press often has in-line drying andfinishing operations.

• Digital - includes toner and ink jet systems; usually printing onto paper, but somesystems enable printing onto polyester film; sheet fed and web configurations;duplex printing capability on most systems; some systems have in-line finishing andbinding operations.

• Flexography - printing from a soft compressible, raised image plate; can print on awide variety of web fed substrates including tissue, paper, corrugated board, foil,metalized paper, and several varieties of plastic; fast-drying, fluid ink; can be config-ured with in-line finishing operations.

• Gravure - printing from a hard, recessed engraved-image cylinder; used to printhigh volume products on a wide variety of substrates including paper, paperboard,foil, plastic films, plastic laminates (e.g. Formica™), and vinyl flooring; cylinderscan average 6 to 7 million impressions.

The factors used to select a print process include:

• Type of product • Quantity• Substrate • Image quality requirements• Image variability requirements • Cost per piece• Color requirements • Turnaround time requirements• Finishing and binding requirements

Many of the print processes are competitive in the same product markets. For example, mag-azines and catalogs may be printed by gravure, offset, and even digital printing processeswith quantity being the primary determining factor. Other products, such as plastic laminate,are exclusively printed by only one process. Variable data can only be done by digital printing.

Xerography vs. Offset LithographyAn important and emerging print market battle exists between xerography and offset lithog-raphy. Quality and affordable full-color printing in short- to medium-run lengths may be bestachieved by digital printing systems. Offset printing can best print specific spot colors. Onlydigital can print variable data. Turnaround time, with immediately dry digital printing, favorsdigital over offset, even on longer print runs. Numerous off-line binding options for cut-sheetfavor both digital and offset, but especially enable fast turnaround on bound, digitally-printedproducts.

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Understanding Color Kenneth F. Hoffmann page 10

Overview of Part Two

Part Two:

How do we see color, anyway?


1. Identify the parts of the human eye and explain their role in color perception.2. Identify visible light as a component of the electromagnetic spectrum.3. Explain the concepts of light absorption and reflection.4. Explain the concept of the temperature of light and the impact on color

perception.5. Explain major physiological and psychological aspects of color perception.

Cold hearted orb that rules the night,Removes the colours from our sight.Red is grey and yellow white,But we decide which is right.And which is an illusion???

The Moody Blues

What is green? Why is the sky blue? What is candy apple red? How do we see color, anyway?In this part you will learn how people perceive color. Most importantly, you will learn whydifferent people see colors differently, and why individuals might see the same color different-ly under different conditions.


AbsorptionColor perceptionConesElectromagnetic radiationElectromagnetic spectrumFatigueKelvinMemory colorNanometersReflectionRodsVisible lightVisible spectrumWavelengths

Part Two: How Do We See Color, Anyway?

1. The human eye2. The electromagnetic

spectrum3. Absorption and reflec-

tion4. The language of color5. Temperature of light6. Physiological factors7. Why do we print in

color?

Part Two:How do we see color, anyway?


The Human EyeTh

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The Rods andCones are on the Retina, thelining on theback of the eye.

The Human EyeThe human eye is the body’s physical receptor of light energy — unless, of course, youinclude the skin when we get sun burns and sun tan. The lens of the eye focuses the light onthe retina, a light-sensitive surface around the back of the eye. The retina is made up of rodsand cones, which are the photosensitive cells. The rods and cones convert the light energyinto different nerve impulses. Vision is a function of light energy reaching the rods andcones.

Did YouKnow?There are around 100 million rods in the reti-na. Rods function in dimlight conditions and pro-duce monochromaticvision: white and blackand shades of gray.

There are more than sixmillion bulbous cones ineach eye. Cones seecolor such as red, green,and blue and also seewhite, black and gray.Cones need higher lev-els of illumination toproduce color vision.

Bright colors at middayare seen as a result ofdifferent wavelengthsstimulating the cones.The same scene in thedarkening dusk appearsmuted, even as shades ofgray, as there is onlyenough light energy tostimulate the rods in theretina.

The eye consists of red-sensitive, blue-sensitive, and green-sensitivecones. It would be extremely unlikely that different individuals havethe same number and distribution of each color-sensitive cone.Therefore, different individuals are unlikely to perceive colorsexactly the same.

Even in a color prepress work environment, with standard viewingconditions, individuals will describe colors different because oftheir differences in color sensitivity.

The eye sees colors in nature that can not be reproduced by anyphotographic or print methods — the eye is the perfect color-sensi-tive photoreceptor!



The Full EM SpectrumTh

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The Electromagnetic SpectrumOur environment is filled with electromagentic radiation. The electromagnetic radiationconsists of a wide range of wavelengths from radio waves to cosmic rays. This range of radia-tion wavelengths is called the electromagnetic spectrum. Visible light is merely the compo-nent of the electromagnetic spectrum that our human eye can perceive.

The wavelengths of energy in the electromagnetic spec-trum range from the extremely short cosmic energy wavesat one billionth of a millimeter to the extremely longwavelengths of radio at more than a kilometer in length.

Telescopes, such as Hubble Space Telescope and ChandraTelescope “see” a lot more than the visible energy in theelectromagnetic spectrum. Sensors can detect energy atalmost all wavelengths: cosmic rays, gamma rays, x-rays,ultraviolet, visible light, infrared, microwave, radar, radio.

The beautiful images from the Hubble Space Telescope arenot always in natural colors. Rather, some of the electro-magnetic energy from the nebulae and galaxies are inter-preted and assigned colors in the visible spectrum for usto enjoy.

Did You Know?Going from the values of radiowaves to those of visible light is likecomparing the thickness of thispage with the distance of the Earthfrom the Sun, which represents anincrease by a factor of a million bil-lion.

Similarly, going from the values ofvisible light to the very much largerones of gamma rays representsanother increase in frequency by afactor of a million billion.

Long Wave Radio Television Microwave Visible Light X-Rays Cosmic Rays

VHF Radio Radar Infrared Ultraviolet Gamma Rays



Visible Light SpectrumTh

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The wavelengths in the visible light portion of of the electromag-netic spectrum range from 380 nanometers (deep violet) to 780nanometers (deep red). A nanometer (nm) is one billionth(1⁄1,000,000,000) of a meter. Visible light is between the ultravioletand infrared energy wavelengths.

We see different wavelengths between 380 nm and 780 nm as dif-ferent colors. When we detect energy wavelengths at 420 - 480 nm,we see blue. When our eyes detect wavelengths around 580 nm wesee greenish-yellow. When we see all of the wavelengths in aboutequal measures, we see “white light”.

The prism can be used to separate white light into the visible spec-trum because the different wavelengths bend and refract at differ-ent angles within the prism.

Did YouKnow?Sir Isaac Newton wasnot the first to believein the theory that whitelight is the sum of allcolors.The Greekphilosopher, Aristotle,believed that white lightwas light in its pristineform.Aristotle believedthat certain color phe-nomena, such as therainbow, arise from amodification of light.

Newton was right aboutlight refraction and thefact that different colorsof light had differentproperties. However,Newton incorrectlybelieved that light wasmade of particles (rays)of matter at differentsizes, rather than thewaves of electromechan-ical energy that weknow today.720 nm The visible light spectrum. 380 nm

Points to Ponder and Debate...There is an age-old question about sound;“If a tree falls in the forest and there is nobody to hear it fall,does the falling tree make any noise?”

Likewise...

If there is no one around to see an object, does that object have any color? If an object is red whenseen in bright light conditions, is the object still red in a darkened room?

Color science states that there is no color without light, an object, the human eye, and an interpretivebrain; all four are necessary for what we call color.



Absorption/ReflectionTh

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Absorption and ReflectionAs white light (the sum of all visible wavelengths) strikes an object, some of the light energywavelengths are absorbed and some of the light energy wavelengths are reflected When white(sun) light strikes the flower petals, the object surface absorbs blue light and reflects greenand red light. We see the mixture of green and red light as yellow.

When red, green, and blue light reflects evenly (or nearlyso) from a surface, then we see that surface as white.



Color PerceptionTh

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Color Perception is Not ExactHuman color perception is not exact. Colors appear different because of their surroundingregions. Two gray squares may be objectively the same, but will appear different based on thedensity or the color of the surrounding regions.

Gradients and shades can often be perceived incorrectly. This is actually an even 20% blackpositioned inside a larger gradient (90% to 10%).

The gray patchsurrounded byyellow appearsdarker than theexact same valuegray surroundedby blue-purple.

The magentapatch surroundedby light grayappears darkerthan the exactsame magentavalue surroundedby dark gray.

The size of anobject affectscolor perception.Colors of largerobjects are moreeasily distinguished.



Language of ColorTh

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HueThe wavelength of light of a particular color in its purest state — without any added black orwhite — is called the hue. The hue in the main attribute of a color that distinguishes itselffrom other colors. The name of the hue itself is a subjective term — different in each lan-guage — that refers to an objectively measured wavelength of radiant energy. Hue is the per-ceived color of an object. Here are some colors in familiar hues.

SaturationThe intensity of a particular hue is called saturation. Saturation refers to the value of a color,the extent to which that color is made of a selected hue rather than of white. Saturation isthe property of a color that makes pale pink different from bright red. The scale for measur-ing and describing saturation ranges from 0% to 100%. We often refer to a color with lowsaturation as looking “washed out”. Saturation can also refer to the amount of grey in acolor. Less grey results in more saturation.

Purple Orange Brown Green Yellow Blue Red

Brightness (also called Lightness, Luminance)Brightness is the amount of light being reflected from a surface. Brightness is the intensityor dullness of a color. A hue in its purest state is at its brightest. In printing, brightness isaffected by the reflectance of the paper.

Brightness also refers to the lightness or dullness of a color due to the kind of light hittingthe object. A barn may be bright red on a sunny day, but a dull red on a rainy, overcastevening. The darker the viewing conditions, the darker are the colors that we perceive.



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What is Green?Few objects in nature either fully absorbor fully reflect the primary colors of red,green, and blue. Therefore, there arenumerous shades of many colors. Green,for example, appears is an infinite varietyof hues. We sometimes call these distinc-tions color shades.

What is a Color Family?The name of a color is sometimes very vague. What is “light blue”? The name may have dif-ferent meaning to different people. Other color names are more specific. What is “navy blue”?In this case the answer would probable be similar from most people: a dark, cool near blackshade of blue.

We have many names for the shades within a given hue. A color family is the colors that arereferred to as being similar in hue. Some members of the Blue family include “Baby”,“Periwinkle”, “Navy”, “Sky”, “Medium”, “Royal”, “Gem”, “Blueberry”, “Aquamarine”,“Cornflower”, “Indigo”, and “Carolina”. Mitsubishi even has a auto color called “Celtic BluePearl” — try describing that one! Every printer knows “Reflex” blue and “Process” blue.

Meet Some Members of the Blue Family



Color and EmotionTh

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Color and EmotionHot, warm, cool, cold: these are words often used to describe colors. We associate tempera-ture, emotions, feelings with colors. We we refer to a color as being “warm” or “cool” wemean an emotional or aesthetic quality, not the actual physical quality of the color or light. Awarm gray is somewhat reddish or yellowish. A cool gray has a blue or green color cast to it.

The early light of dawn casts a warm glowon this mountain lake scene.

The deep green forest fern bed suggests a coolatmosphere on even the hottest day.

The blue cast on this wintry landscape makesit feel even colder than the snow itself might suggest to the viewer.

You don’t need a desert to evokethe feeling of a hot location.



Color and EmotionTh

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Physiological Responses to ColorOur bodies respond differently to different colors that we see. For example:

• RED increases electroencephalographic activity, chronic tension,muscular activity, eye blinks

• BLUE decreases all of the above.

These physiological responses to color is probably whyblue is considered a “professional” color that communi-

cates calmness and control. Blues is a popu-lar color in corporate logos and for cor-porate uniforms.

Red effectively calls attention to criti-cal information and to danger warn-

ings in communications. Red is often usedfor emphasis in package labels and signage.

Emotional Responses to ColorThe most intense emotional responses are associated with bright colors at both ends of thevisible spectrum (red and purple).

Warm colors, such as reds, oranges, and yellows, are used to represent action, vitality, fun.They can denote aggressiveness and appear close.

Cool colors, such as blues and greens, are seen as restful and quiet. They represent status,background information, and work. They denote calming assurance and appear remote.

But, there are cultural differences. In France, red is associated with aristocracy; in Japan, yel-low is associated with nobility and grace. Some holidays have strong color associations.Valentine’s Day: red, pink. Easter: purple, white, yellow. St. Patrick’s Day: green. Halloween:orange, black. Christmas: red, green.

Infants and young children choose bright, saturated colors. Adults prefer more desaturatedcolors as they grow older. Blue is the most universally liked and recognized color, evenamong those who are color-impaired.



Physiological FactorsTh

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The Physiological Factors of Color PerceptionIn the imaging and publishing field, we must understand color compres-sion. The human eye can see over nine million colors; color film only10,000 to 15,000; the sheetfed press only 5000 to 6000; and the web presscan only deliver 2000 to 3000 colors. Nothing that we produce as a photoor a printed sheet will ever exactly match the colors in the real world.

Vision is susceptible to sensory adaptation. There is a reduction in sensi-tivity to stimulation as the stimulus persists for a period of time — stayout in bright sunlight, eyes become less sensitive; your eyes will take timeto adapt to a sudden change such as entering a dark room. Likewise, thereis an increase in sensitivity when there is a lack of stimulation — when ina dark room for a while the eye becomes sensitive to very low levels oflight energy.

There are also physical differences in color vision: people see and describecolor differently per one's own sensitivity. Subjective differences mayresult from physical adaptation over time: production workers on dayshifts may perceive color differently than the night shift crew. Describingcolor is difficult due to the lack of a standard vocabulary or set of terms toexplain visual differences — a fact often overlooked in making colorapprovals or describing color corrections.

Aging is a real factor. The need for increased illumination is greater as oneages. A person at age 50 may need 50% more illumination than whenhe/she was age 20.

We cannot memorize color or tonal gradation: we can only compare colorunder a standard light source. Color can appear unchanged even underdifferent conditions. White and object colors that are part of a color scenemay still appear the same under different lighting conditions — whatappears as a white surface may in fact be a light gray when compared toother white values. The eye focuses on contrast and context rather thanmemory.

Color fatigue is the cause of the negative afterimage from over stimula-tion. Stare at a color for a minute and quickly look away and you often geta negative (opposite color) afterimage floating, for a few seconds, in yournew field of vision. Color fatigue increases in effect when person becomestired or mentally exhausted This phenomenon will vary from individual toindividual but we are all affected and should be aware of the potentialwhen doing color evaluations. The negative afterimage from color fatigueimpacts the visual evaluation of color or hue.

Adaptation toStimulus

Aging is a RealFactor

No ColorMemory

Color Fatigue

ColorCompression

People See andDescribe ColorDifferently



Temperature of LightTh

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Temperature of LightColor temperature, measured in degrees Kelvin, is the temperature to which a black objectmust be heated to produce a certain color light. As an object is heated, it emits radiation of acharacteristic color. Color temperature is a system of numbers used for measuring the colorof light. The color varies according to its temperature which is measured in degrees Kelvin.

Candle light, at 1800°K, has emitted radiation that is relatively red. 2900°K is representative ofa tungsten lamp. At 4800°K, light is relatively yellow. At 6500°K the color of light is neutraldue to an even distribution of wavelengths. At 9300°K, the color of light is relatively blue.

5000°K is close to the color temperature of direct sunlight and is considered the standardlight temperature for viewing conditions during color evaluation for the imaging, publishing,and printing industry.

KelvinScaleThe Kelvin Scale(abbreviated bythe letter K) is asystem of absolutetemperatureinvented byWilliam ThompsonKelvin.The Kelvinscale uses thesame degrees asthe Celsius (C)scale, but definesabsolute zero(0°K) as the tem-perature at whichall atomic activitystops.

0°Kelvin = minus273.16°Celsius.Numerically, theKelvin tempera-ture is equal tothe Celsius tem-perature plus 273degrees.

This imageappears as itwould understandard 5000°Kcolor evaluationand viewingconditions.

This imageappears with agreenish color

cast as it wouldunder standard

fluorescentlight viewing

conditions.

The color temperature of the viewing conditions will directly impact theappearance of the photo, proof, or printed sheet being evaluated.



Why Do We Print in Color?Th

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Why Do We Print in Color, Anyway?While color is not necessary for visual communication, studies have clearly shown the manyadvantages of added color in documents. Color can add significant impact to a design. Colorcan increase the effectiveness of print/media communication. Color can add interest.

Marketing studies have clearly shown that the use of color results in return rates significant-ly higher than those for black& white printing. Sometimes the results with color images canbe ten or more times higher than black and white printing.

This illustrationmay be consid-ered as moreeffective in colorthan when ingrayscale.

Many magazineadvertisementsare printed ingrayscale andare very effective.

Would thisposter be asappealing andinteresting with-out the use ofcolor?

Overall, color isproven to be amore effectivecommunicationstrategy thangrayscale orblack & white.

Cambria Museum of ArtJoin us for an evening of live music, refreshment, and art in celebration of our new location at the heart of downtown Cambria. Featuring a true Cambria treasure: 100 years of local artwork.

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Research has proven that using color in business documents can have measurable results. The following examples have been selected from a variety of sources to demonstrate the power that black and white documents can achieve when printed in color.

Color Captures Attention➥ Color emphasizes critical information and conveys a sense of

professionalism

➥ Color increases readers’ attention spans and recall by 82%

➥ Color gains readership by 80%

➥ Color makes an impression that is 39% more memorable

➥ Telephone listings printed in color can increase response by 44%

➥ People are more likely to pick up a full color piece of mail first.

➥ Color emphasizes critical information and conveys a sense ofprofessionalism

Color Improves Communications➥ Color increases comprehension by as much as 73%

➥ Color speeds learning and retention by 78%

➥ Color can boost survey participation by 80%

➥ Reader comprehension has been found to be 14% better withhighlight color rather than with bold text

Color Sells➥ Color helps sell up to 80% more

➥ Color can improve brand recognition by up to 80%

Color increasesreader’s attentionspans and recall by82%.

➯82%

Color speeds learn-ing and retentionby 78%.

➯78%

Color helps sell upto 80% more.

➯80%




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Color Enhances Productivity➥ Color reduces search time by as much as 80%

➥ Color reduces errors by 80%

➥ Information can be located 70% faster if it is in color

➥ Document sorting improves by 15% when highlight color is used

➥ Highlight color improves search time by 39% when compared tousing different fonts

➥ Color can increase payment response by up to 30%

➥ People are 2.5% more likely to pay the full amount when it isshown in color.

Color increasesreader’s attentionspans and recall by82%.

➯82%

Color Attracts Attention

Color Clarifies

Color Sells

Part Three:Comparative Color Models


Overview of Part ThreeTh

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Part Three:

Comparative Color Models


1. Explain the principles and application of additive color model.2. Explain the principles and application of subtractive color model.3. Explain the principles and application of the artist’s color wheel.4. Explain the principles and application of the CIE color models.5. Explain the principles and application of the Munsell Color System.

Understanding color and how it isreproduced is one of the most difficultconcepts in the graphic arts, but it isalso one of the most rewarding tounderstand.

Thomas E. Schildgen

Over the years, the ability to understand, visualize, communicate, and reproduce color hasbeen analyzed and defined. We have used scientific, perceptive, quantitative, and qualitativedescriptors and measures. Fundamentally, color is a human sensation and the business ofcolor remains a subjective evaluation by the customer.


Mixing SystemsAdditive colorSubtractive color RGBCMYKPrimarySecondaryTertiaryIntermediateComplementaryColor wheelCIEChromaticityChromaticity diagramGamutMunsell Color SystemPerceptual Chroma

Part Three: Comparative Color Models

1. Additive Color: RGB

2. Subtractive Color: CMYK

3. Artist’s Color Wheel

4. CIE color models

5. Munsel Color



Additive Color ModelTh

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nly. The Additive Color Model

We see light. The additive color model buildscolor with light. Televisions and computermonitors build color with the additive colormodel. The additive color model is oftenreferred to as “RGB Color” because the three

primary colors are Red, Green, and Blue.Each of these three primary colors is one-third of the visible light spectrum. As theamounts (intensity) of RGB lights are varied,new colors are made. A RGB monitor can dis-play millions of colors, all made from combi-nations of only red, green, and blue lights.

To best understand the additive colormodel, imagine a white wall in a dark-ened room.

A beam of red light makes a circle on thewhite wall — a RED circle, of course.

A beam of blue light makes a BLUE circlethat overlaps the red circle. In the areawhere red and blue overlap, a new,lighter color is made. This new color has2/3 of the visible light spectrum and isnamed MAGENTA. (R + B = Magenta)There is no green in magenta.

A beam of green light makes a GREENcircle that overlaps the blue and red cir-cles. In the area where green and blueoverlap, a new, lighter color is made. Thisnew color has 2/3 of the visible lightspectrum and is named CYAN. (G + B = Cyan) There is no red in cyan.

In the area where green and red overlap,a new, lighter color is made. This newcolor has 2/3 of the visible light spectrumand is named YELLOW. (G + R = Yellow)There is no blue in yellow.

In the area where red, green and blueoverlap, a new, lighter color is made. Thisnew color has all of the visible light spec-trum and is named WHITE. (R + G + B =White)

Additive Color Model

Primary ColorsRed, Green, Blue

Secondary ColorsRed + Blue = Magenta Blue + Green = Cyan Red + Green = Yellow

Red + Green + Blue = White

In both print and non-print media, we mix some colors to make additional colors. There aretwo widely used “mixing systems”: the additive color model and the subtractive color model.



Subtractive Color ModelTh

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The Subtractive Color ModelWe see light. But, we do not print with light.Printing systems use the subtractive colormodel by subtracting color from white light.The subtractive color model is often referredto as “CMYK Color” because the three sub-tractive primary colors are Cyan, Magenta,and Yellow. Each of these three primary col-

ors subtracts one-third of the visible lightspectrum. Black is used as a correcting colorto add neutral density to the colors. As theamounts (coverage area) of CMYK inks ortoners are varied and mixed, new colors aremade. A CMYK color mixing and printingsystem can make millions of colors, all madefrom combinations of only cyan, magenta,yellow, and black.

To best understand the subtractivecolor model, imagine a white sheetof paper in a white lighted room.

A patch of CYAN ink makes a cyansquare on the paper. We see cyanbecause the red has been subtractedfrom the reflected light.

A patch of MAGENTA ink makes amagenta square on the paper. Wesee cyan because the green hasbeen subtracted from the reflectedlight. Where the cyan and magentaoverlap we see BLUE, because all ofthe red and green have been sub-tracted from the reflected light.

A patch of YELLOW ink makes ayellow square on the paper. We seeyellow because the blue has beensubtracted from the reflected light.Where the yellow and magentaoverlap we see RED, because all ofthe blue and green have been sub-tracted from the reflected light.

Where the yellow and cyan overlapwe see GREEN, because all of theblue and red have been subtractedfrom the reflected light.

Where all three colors (CMY) over-lap, the result is almost black. Blackis used as a fourth color to add neu-tral density. Black is indicated bythe letter “K”; “B” is for blue.

Subtractive Color ModelPrimary Colors

Cyan, Magenta, Yellow

Secondary ColorsCyan + Magenta = BlueCyan + Yellow = GreenMagenta + Yellow = Red

C + M + Y = (almost black)Black (K) is used to increase density.

A primary color is one that cannotbe made by mixing two other colors,but, theoretically, primary colors canbe mixed to produce other colors.

A secondary color is one that results fromthe mixing of two primary colors.

A tertiary color (sometimes called intermedi-ate color) results from the combination of asecondary and a primary color. For a tertiary

color mix, the name of the primary color isgiven first.

The artist may use the color wheel to helpplan a design. The color directly opposite anyselected color on the wheel is called a com-plementary color. Complementary colorswould go together well in design.



Artist’s Color WheelTh

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Primary ColorsRed, Blue, Yellow

Secondary ColorsOrange, Green, Purple

Tertiary ColorsYellow-Orange Blue-PurpleYellow-Green Red-PurpleBlue-Green Red-Orange

The Artist’s Color WheelPerhaps, you remember a different colormodel from art class. Called the Artist’s ColorWheel, this model shows red, yellow, andblue as the primary colors. A color wheel isa visual reference chart of colors.

The colors on the color wheel are calledhues. They are divided into primary, secondary, and tertiary colors. The left side ofthe wheel (Yellow through Red-Purple) arereferred to as “warm” colors. The right sideof the wheel (Yellow-Green through Purple)are called the “cool” colors.

The artist Marc Chagall said, “All colors are the friends of their neighbors and the lovers of their opposites.”

P

P

S

S S

TT

T Neutral T

TT

P

Did You Know?The Jesuit teacher François d'Aguilon,in 1613, declared that there were threeprimary colors: red, yellow, blue, whichtogether with white and black could becombined to make all colors.

Sir Isaac Newton not only studied thevisible light spectrum, he also arrangedto colors of the spectrum into a circleto study the colors. Many color wheelshave since been developed.This colorwheel was defined by Herbert Ives,based on the work of Newton.

With the simple use of shades,tones, and tints, shapes can begiven a three-dimensionalappearance.



Artist’s Color WheelTh

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Y

M

B

G R

II

I Neutral I

II

C

Alternate Artist’s Color Wheel and Color TrianglesIn various art texts the color wheel has different variations. Below is a common color wheelthat combines and emphasizes the RGB and CMY colors. Which are the primary colors andwhich are the secondary colors depends on which model (additive or subtractive) is empha-sized. The mixture of the primary and secondary colors are called Intermediate colors.

The concept of complementary colors is often expanded. Oppositecolors on the color wheel are calledcomplementary.

Near complements are colors whichalign in a “Y” pattern in the wheel.An example is indicated by themagenta lines. Twelve different “Y”patterns can be made to define 12different near complement groups.

Triadic complements are formed ina triangular pattern, as indicated bythe cyan lines. Four different triadiccomplement groups can be defined.

Near and triadic complements areformed on both the standard andthe alternate artist’s color wheels.

Artist’s may use a color triangle to showcolor shades (intermediates between a hueand a black), tints (intermediates betweena hue and white), and tones (intermedi-ates between a hue and gray).



CIETh

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CIE Color ModelsCIE is the abbreviation for CommissionInternationale de l’Eclairage (InternationalCommission on Illumination), an organiza-tion that defined a visual color model in1931. This group established specificationsfor the standard observer color vision sensi-tivity. Their work in 1931 established whathas become the most universally acceptedsystem of color measurement.

The CIE system developed a device-indepen-dent, uniform color model. The CIE systemhas evolved into four different color spaces tomeet the needs of different market sectors.

The measurements used by the CIE werebased on a standard observer. The CIE

sampled 1,700 individuals to establish a stan-dard red, green, and blue wavelength of lightthat represented the average observer.

A chromaticity diagram is a two-dimensionalplotting of the CIE three-dimensional colorspace. The 1931 CIE-XYZ diagram (left) wasdeveloped to show the entire gamut (range)of perceivable colors, expressed in chromatic-ity. Chromaticity is a color quality of lightthat is defined by wavelength and saturation,independent of brightness or luminance.

A significant and frequently used applicationof the CIE-XYZ diagram is its adaptation(right) to show the relative gamut for colorsthat can be reproduced on photographic film,on a computer monitor, and on an offsetprinting press.

520

510

500

490

480

470460

450 400-380

530

540

550

560

570

580

590600

610620

630650

700-750

Film

Monitor

PrintingPress

Did You Know?James Maxwell, a Scottish physicist, brought mathematics to the search for a color model. In 1872, hedeveloped an equilateral triangle chart that placed the three primary colors (RGB) at the corners. Hestated that all color could be located within the triangle. His work is the basis for the 1931CIE system.

CIE model in 1931.Wavelength numbers

are in nanometers



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In 1976, in an effortto better refine colormeasurement,CIELAB and CIE LUVwere developed.

CIE LAB (also knownas CIE L*a*b*) isbased on CIE XYZ.The L* values repre-sent lightness. Thechromaticity coordi-nates are indicated bya* and b* — a* is thegreen/red and b*indicates the blue/yellow. The CIE LABmodel is used pri-marily for reflectivecolor, includingprinted sheets.

The CIE LUV color spacemodel is very similar to theCIE LAB model. The CIELUV model is primarilyused for TV and computermonitor displays.

L=100white

(+u*)+a*red

(-u*)-a*

green

(-v*)-b*

blue

(+v*)+b* yellow

L= 0black

L*value

Yellow+ b*

Hue

40

50 60

Blue- b*

Green- a*

Red + a*

30

20 10

simulation

In the Munsellcolor system,the ten hueregions arearranged socomplementcolors are oppo-site each other.

Munsell identi-fied five mainhues:

Red (R), Yellow (Y)Green (G)Blue (B)Purple (P)

Five intermedi-ate hues are:

Yellow-Red (YR), Green-Yellow (GY)Blue-Green (BG)Purple-Blue (PB)Red-Purple (RP)

Steps inbetween these hues are given a number from 1 to 10 preceding the letter, as in 5R or 4.5PB.The value or lightness of a color ranges from 1 to 10, in perceptually uniform steps. The

chroma or saturation of a color also is arranged in perceptually uniform steps. The maximumchroma differs for each Munsell hue, ranging as high as 15 for the yellows and 16 for thereds. Neutral whites, grays, and blacks have a chroma of zero.

The three attributes of the Munsell color system — hue, value, chroma — are given in anotation form “HV/C.” For example, the notation 7.5RP 8/10 would indicate a color 7.5 stepsaround the color wheel from the red-purple, of medium-high brightness, and high saturation.



Munsell ColorTh

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The Munsell Color SystemThe Munsell Color System is a perceptualcolor system that defines colors by hue,value, and chroma. Introduced in 1913 byAlbert H. Munsell, and American artist andteacher, used chips of color for visual refer-ence and identification.

Called the Munsell Color Tree, the modeluses a vertical axis to represent the lightnessor value of a color, and the horizontal axis torepresent the chroma or saturation of acolor. The purest color is located on theouter edge of the model. Ten hue regions arearranged in a circle around the brightness/lightness value axis.

white

blue-green

red-purple

yellow-red

red

yellow

blue

purple-blue

purple

green

green-yellow

9

8

7

6

46

810

5

4

2

1

black

chroma

valu

ehue

Part Four:What is Color Separation?


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Part Four:

What is Color Separation?


1. Identify and describe the function of the primary component parts in scannersand digital cameras.

2. Explain the color concepts of process color separation.3. Explain the basic procedures in preparing color images for best print quality.4. Explain the role of the halftone dot and stochastic screening spot.5. Explain how halftone and stochastic images are made in PostScript.6. Explain the concept of dot gain.

A good scan is as important as a goodoriginal to successful reproduction ofan image; neither digital retouchingnor high-quality output can make upfor an inadequate scan.

Agfa, “A Guide to Color Separation”

How do colors separate? How do we put them back together again? Why are we always beingcorrected? What are we screening for? How does your dot grow? To moiré or not to moiré: isthat an option? How many pixels do you need to make a dot? Or, is that how many dots makea spot? Color separation: an art, a craft, a science, or a technology — or all of the above?


scanners drum scannersflatbed scanners analogdigital linear arraymatrix array megapixelA/D conversion binarybit depth process colorcolor separation tone reproductiongray balance color correctionhalftone screen anglescreen frequency dot sizedot shape misregistrationalgorithm stochastic screeningdot gain FM screeningoptical dot gain

Part Four: What is Color Separation?

1. Image capture: colorscanners and digital cameras

2. CMYK printing process3. Steps to good color4. The function of ink and

toner on paper5. The halftone dot6. Stochastic screening7. Dot gain



Image Capture: Color ScannersTh

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How Do Scanners Work?A scanner uses a light source, optics (mirrors and lenses), and filters (RGB). The scannermeasures the RGB color values of light that reflect off the image (for reflective photographs orart) or shine through the image (for slides/transparencies). The scanner records those valuesin an electronic file with data for each of the three RGB channels. As the image is measured,each sample point is recorded as a separate pixel (picture element) comprised of the differentvalues of RGB light. The resulting bitmap of the pixelized image can be reconstructed on acomputer screen.

PMT - Photomultiplier Tube

Drum scanners, in which the flexible film orprint original is mounted on a rotating glassdrum, use three (RGB) PMT sensors whichconvert light into voltages or electricalcharges. These electrical charges are analog,continuous signals of varying intensity. ThePMT can sense very low light levels by ampli-fying the signals during the sensing. The sig-nals are converted into a digital form andsent to the computer for image display andfile storage.

Drum scanners, using PMT technology, arecapable of registering a wide density rangeand for many years were the standard forhigh quality color separation scans in thepublishing industry. However, PMT scannershave very high manufacturing and mainte-nance costs due to their complexity.Extensive manual controls in most PMTscanners require the operator to have a veryhigh level of knowledge and expertise.

Because of the curved surface and high-speedspinning of the scanner drum on which thefilm or print is mounted, only flexible mate-rials are supported. Rigid originals must becopied onto film. Precious flexible originalswere often duplicated to avoid any risk ofdamage during scanning. Many color separa-tions were made from second-generationimages. Therefore, drum scanners have oftenbeen replaced by the top-of-the line flatbedscanners in many production environments.

PMT - Photomultiplier Tube Scanners

Advantages

✔ High speed

✔ Wide density range

✔ High resolution

✔ Preview accuracy

✔ Preview-level color control

✔ Preview-level sharpening control

✔ File format choices

✔ Reflection and transparency

✔ Interchangeable drums for off-scanner image mounting

Disadvantages

✘ Proprietary high-cost systems athigh end of market

✘ Mounting flexible images is time-consuming

✘ High operator knowledge andskill required

✘ Risk to original on spinning drum

✘ Cannot scan rigid originals

Current Market Status

➘ Rapidly declining market share

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Part Four:What is Color Separation? Image Capture: Color Scanners

CCD - Charge-Coupled Device

Flatbed scanners, in which the copy isplaced on a glass plate, use triple-array,RGB-filtered, light capturing CCD elements.CCD's are semiconductor chips that convertlight into voltages or electrical charges.These electrical charges are analog, contin-uous signals of varying intensity. The inten-sity is relative to the strength of the lightthat hits the sample point on the CCD array.The signals are converted into a digital formand sent to the computer for image displayand file storage.

Flatbed scanner CCD technology at the endof 1999 is a very mature technology. Thehigh-end flatbed scanners register densityranges that match or exceed drum scanners.Once considered poor quality and slowspeed compared to drum scanners, CCDflatbed scanners are now the most widelyused scanners. Scanner resolutions, optics,software, consistency, and speed have all sig-nificantly improved in recent years.

Software controlling the flatbed scannerstoday enables one to make scans withoutrequiring a high level of color knowledgeand expertise.

Flatbed CCD color scanners today rangefrom nicely capable home and office devicescosting under $200 to mid-range professionalscanners costing around $8,000 to high-endprofessional scanners costing around$50,000. Quality, versatility, and productivitydetermine the cost and appropriate use.

Evolution of the Scanner1970: $400,000.00 scanner with a free computer as part of its system!

1999: $1,500.00 computer with a free scanner!

CCD - Charge-Coupled Device Scanners

Advantages

✔ Wide range of devices for manymarkets and budgets

✔ Density ranges from 24-bit to 48-bit

✔ Improved optics

✔ Improved user-friendly software

✔ Reflection and transparency nowon most scanners

✔ 3D object scans on some models

✔ Dedicated slide scanners

✔ Wide range of flatbed sizes

✔ Increasing automation of scan-ning process.

✔ High productivity levels of top-of-line scanners

Disadvantages

✘ Diversity of market choices forscanners can lead to purchase ofscanner with capabilities whicheither do not meet or exceedneeds of user.

Current Market Status

➚ Rapidly increasing market sharedue to range of device featuresand overall decreasing cost ofhighly-capable scanners.



Image Capture: Digital CamerasTh

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How Do Digital Cameras Work?Digital photography usually includes traditional camera optic and mechanisms, but uses elec-tronic light sensors rather than film. Many digital cameras have unique camera bodiesdesigned especially for their digital purpose. Other digital cameras are built with camera bod-ies that fully utilize the same lenses as conventional film cameras. Studio cameras use inter-changeable conventional film and digital camera backs for total versatility and economy.

Digital cameras are becom-ing an increasingly impor-tant component of a fullydigital publishing and print-ing workflow, as shown inthis workflow diagram.

A digital camera can bedescribed as “a scanner witha lens in front.” Digitalcameras use CCD light sens-ing elements. The CCD’s arecomposed of thousands ofminute elements in a lineararray (grouped in a row) ormatrix array (grouped inrectangular block).

Linear arrays are moved insteps across the image planeof the camera and are oftenused for capturing high-res-olution images of non-mov-ing subjects.

Matrix arrays, also known asarea arrays, capture the fullscene in a fraction of a sec-ond, permitting subjectmovement. Both types ofarrays include RGB filters tomake the color channels.Matrix arrays are oftendescribed by total pixels aswell as by width and heightpixel measurements.

Do You Know?How many pixels equals a “megapixel”? (One million pixels)

How do you calculate a megapixel? The Nikon D1 camera model has a2.74-megapixel CCD for ultrahigh-definition images.This cameramakes an image with a resolution of 2,012 x 1,324 effective pixels(2,663,888 pixels = 2.66 megapixels).

A Typical Digital Workflow for Publishing

Text and Image AcquisitionText - word processing

Graphics - computer illustrations

Photos - digital cameras

Digital Document Creation

Digital Proofing

Digital Printing



A/D ConversionTh

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Analog to Digital (A/D)ConversionThe conversion of an analog (continuous)signal into its digital (discrete) equivalentis essential. Computers can only display,manipulate, and store digital data. TheA/D converter measures input voltage andoutputs a digitally encoded number cor-responding to that voltage.

Counting in binary format (zeros andones) an 8-bit converter can sample 256gray levels (0 through 255 — 00000000through 11111111).

Pixels in an RGB image requires an 8-bitnumber for each color channel, offering agamut of 16.7 million colors (256 x 256 x256). the resulting 24-bit RGB imagerequires three times the storage space ofthe monochrome image. When an RGBfile is converted to a CMYK file forprocess color printing, four 8-bit chan-nels are created from the previous three,making a 32-bit depth file.

Scanners and digital cameras do not make theRGB to CMYK conversion. This conversion isdone by image editing software applications orutilities.

Shopping for Scanners and Digital CamerasWhen shopping for a color scanner or a digital camera, many issues are very similar:

Resolution - how much image data is sampled.This determines the detail of any image that is cap-tured and the enlargement potential of any image for a given output requirement.

Bit depth - how many tones and colors can be recognized and recorded.

Optics (lenses and mirrors) - the quality of the optics determine such important factors as imagesharpness and light-level sensitivity.

Speed - the productivity of the scanner (scan time) and the digital camera (frames per second).

Scanner considerations also include reflection/transparency and size of scanning area. Digital cameraconsiderations include lens types and options, viewing, relative shutter speeds and f-stops, and memorystorage and image file downloading.

Use the Internet to search for various color scanner and digital camera manufactures. Compare fea-tures and costs.You will find a very wide range of scanner and camera models. Digital cameras and colorscanners are becoming increasingly more capable at steadily decreasing costs.

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Analog Digital



Process Color PrintingTh

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Cyan

blacK CMYK

C + M C + M + Y

Magenta Yellow

Process Color PrintingPrinting full-color pictures with inks or tonersuses the subtractive color model (CMYK). Eachlayer of color subtracts color reflecting from thepaper. The amount of color subtracted depends onthe size of the spots of printing ink or toner.



Steps to Good ColorTh

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Steps to Good Color ReproductionOptimum color reproduction depends on three elements:

1. Tone reproduction — image contrast, highlight, midtone, and shadow densities2. Gray balance (cast correction) — adjusting the proportions of CMY to produce a

neutral gray.3. Color correction — achieving accurate hue and realistic saturation

Tone and gray balance corrections must be accomplished before color correction is attempted.Unsharp masking followed by RGB to CMYK conversion, if needed, complete the process.

original image

sharpened

color corrected

tone & cast corrected

Cyan ink or toner on papersubtracts red light. (theremaining light reflectionsare: B + G = Cyan)



Ink/Toner on PaperTh

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Function of Ink/Toner on Paper in ProcessColor PrintingThe three primary colors of white light are Red, Green, and Blue.White paper reflects all three colors evenly.

Cyan and magenta ink ortoner on paper subtractsboth red and green light.(the remaining light reflec-tions is Blue

So, Why do We Need Black?Theory and Reality do not match exactly. The CMY inks and tonersare not pure colors. The slight imperfections mean that some lightstill reflects off of the paper. These slight imperfections cause somelight to reflect off of the sheet. The result is a less-than-pure black.

Ink and toner act like a filter on the surface of the paper. Color layers each filter out (absorb,subtract) some color from the reflection of light off of the paper surface.

Fast FactoidThe dye, magenta, invented in 1859, was namedin honor of Napoleon III’s victory over Austriaat the Lombard town of Magenta, Italy.



The Halftone DotTh

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Halftone Dots (Spots) in Process Color PrintingA conventional or digital printing press has inks and toners each with a single density. Aprinter varies the amount of cyan, magenta, yellow, and black ink/toner coverage by usingdots or spots, all with the same density.

We just learned that ink and toner act like a filter on the surface of the paper and that thesecolor layers each filter out (absorb, subtract) some color from the reflection of light off of thepaper surface. The size of the CMYK dots or spots of coverage determines how much RGBlight is subtracted from the reflected light.

The most common method for controlling ink coverage is the conventional halftone.

In conventional halftones, the image is made of vary-ing-size, evenly-spaced, equal density dots which createthe illusion of a gradation of tones.

The four primary characteristics of halftones include:screen anglescreen frequencydot sizedot shape.

Screen Angles

In process color printing, each color halftone at madewith its dot pattern at a different angle.

In conventional color separations, the halftone screenangles are black at 45°, magenta at 75°, cyan at 105°,and yellow at 90°. (Figure A)

Incorrect screen angles will result in a moiré pattern— an unwanted interference pattern caused by varia-tions in the way the color halftone dots overlap.(Figure B)

Misregistration of the halftones will result in blurryimage detail and possible color shifts since the halftonedots do not line up and overlap correctly. (Figure C)

A

B

C

K=45°

M=75°

C=105°

Y=90°

K=45°

M=75°(shiftedright)

C=105°

Y=90°

K=45°

M=55°

C=105°

Y=90°



The Halftone DotTh

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Dot Size

Halftone dot size is stated in terms of percent dot area — the percentage of the area that iscovered by ink. Screen tints use the same terminology.

A binary digital printing system renders a halftone by controlling the placement of the printerdots on the substrate. The size of the halftone dot is constructed point by point or pixel bypixel. This is true of imagesetter films, printing plates, and laser printed sheets.

The resolution of the rasterized page is defined as pixels per inch or dots per inch. The entirepage is comprised of addressable pixels in a grid pattern (bitmap). Halftone dots are defined assections of the page’s grid pattern; these grid sections for each halftone dot are called cells.The total number of imaged pixels, divided by the total number of pixels in each halftone cell,is the percent dot area for that specific halftone dot.

Below are simulated halftone cells with imaged pixels that are clustered to make the individ-ual halftone dots.

4/256 = 1.5% 104/256 = 40.6% 216/256 = 84.3%

Screen Frequency

Screen frequency is the count of parallel lines or rows of dots per unit of measure: lines perinch or lines (lpi) per centimeter (L/cm). The higher the number of halftone dots per inch,the greater the amount of image detail that can be rendered. The screen frequency is chosenafter considering print method, resolution, and substrate.



The Halftone DotTh

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Dot Shape

In conventional (photographic process) halftones, the halftone dot was made as light passedthrough a halftone screen film. Dots “grew” outward, evenly from a center core. Halftonescreens were made with round, elliptical, or square dot shapes at the 50% midpoint dot size.Different shapes yield different results in varying print conditions. For example, round dotsare preferred over elliptical dots in web offset printing because of the potential for slightstretching of the dot shape.

In digital halftone rendering with dots that are built pixel by pixel, the possible shapes aremany. With PostScript halftone rendering, each pixel at the output device resolution isaddressed and controlled. Therefore, a wide variety of dot shapes are possible. Screen fre-quency, output device resolution, and screen angle are all factors in dot shape.

A

B C

Dot Shapes and PostScriptPostScript must address each pixel on thepage bitmap.All pixels must be used.Thehalftone cell easily aligns to the bitmap gridat both the 90° and the 45° screen angles.Figure A shows a 10 x 10 cell at 90°.

In Figure B, the same size cell does not alignto the grid at the 75° screen angle.

Figure C simulates how PostScript will adjustthe cell shape to fit the bitmap grid at thebest possible screen angle and nearestscreen frequency.

Imagesetter and platesetter vendors havetheir own screening algorithms to get thebest dot shapes with their systems.



Stochastic ScreeningTh

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Stochastic ScreeningIn conventional halftones, the dots are evenly spaced and vary in size. Stochastic screeninguses same-sized micro dots that are precisely placed in a way that seems randomly spaced.Stochastic screening will render a photographic image with much higher detail than conven-tional screening because of the smaller image elements.

The algorithm (mathematical calculation) that controls stochastic screening dot placementuses information about the image densities, output device resolution, and minimum dot size(usually the printer’s resolution setting. The grayscale image density is recreated in print by aseemingly random distribution of the imaged pixels. (see figures in the box below).

Many digital printers provide the option to render images in a “photographic” or continuoustone mode. These printers use a method called diffusion dithering which, in effect, is verysimilar to stochastic screening, rather than printing with the geometric grid pattern of con-ventional halftones. The result is smoother images with higher amount of detail.

The terms photographic and continuous tone are actually misused since the printed imagesare built with four toner colors (CMYK), each with consistent density. The photographicimages throughout this curriculum course book are imaged with a digital printer using the“photographic” or continuous tone option.

4/256 = 1.5% 104/256 = 40.6% 216/256 = 84.3%

4/256 = 1.5% 104/256 = 40.6% 216/256 = 84.3%



Dot GainTh

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Ink and Toner Printing Difference: Dot Gain IssueIn offset printing, there is a phenomenon called dot gain. Essentially, the halftone dot size onthe printed sheet is larger than the dot size on the offset plate. Dot gain is caused by fourmajor factors, some are more important than others depending on the specific situation.

- the inking of the plate: a dot with ink is slightly larger than a dot without ink- the pressures of transferring the ink from plate to blanket to paper- the absorption or spread of ink on the paper- the color light spread within the paper (optical dot gain) makes the dot appear larger

than it really is.

Dot gain is inevitable; dot gain cannot be eliminated in offset printing. However, dot gain canbe calibrated and controlled. When dot gain is out of control (such as in the magenta ink onthe image below) then a color shift will occur.

Digital printing with toner spots does not have true dot gain. There is not a plate to compare“before and after” dots. However, each digital printing device does have its unique printgamut — the range of colors which it can reproduce.

Optical dot gain is caused by theshadow of the color ink or tonerwithin the paper. Therefore, thepaper — as well as the printingmethod — is a factor in overalldot gain or color appearance.

Dot gain can be measured and com-pensated for in prepress procedures.

Desired Dot Area On Press Sheet

Prepress On Press Sheet

Uncompensated

Compensated

Simulated “Good” Dot Gain Simulated “Excessive” Dot Gain



GCR and UCRTh

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GCR and UCR Color ReplacementWhen we print color separations, the three additive colors (red, green, and blue) are translat-ed into their subtractive counterparts (cyan, magenta, and yellow). In theory, equal parts ofcyan, magenta, and yellow would combine to subtract all light reflected from the paper andresult in black. However, due to printing papers, print conditions, and impurities present inall printing inks, a mix of 100% CMY instead yields a muddy brown. In standard color separa-tion CMYK printing, black ink or toner is used to add neutral density and increase the depthof shadow colors.

In addition, many printers remove some cyan, magenta, and yellow in areas where the threecolors exist in equal amounts, and they add black ink. Prepress operators typically use one oftwo ways to generate black in print: gray component replacement (GCR) or undercolorremoval (UCR):

• With GCR, black ink is used to replace portions of cyan, magenta, and yellow ink incolored areas as well as in neutral areas. GCR separations tend to reproduce dark,saturated colors somewhat better than UCR separations do and maintain gray bal-ance better on press.

• With UCR, black ink is used to replace cyan, magenta, and yellow ink in neutralareas only (that is, areas with equal amounts of cyan, magenta, and yellow). Thisresults in less ink and greater depth in shadows. Because it uses less ink, UCR isgenerally used for newsprint and uncoated stock.

UCA (undercoloraddition) compen-sates for the loss ofink density in neu-tral shadow areas.This additional inkproduces rich, darkshadows in areasthat might appearflat if printed withonly black ink. Thisoption is availableonly for GCR separa-tions.

Increasing the UCAamount increasesthe amount of CMYadded to shadowareas.

Part Five:Working with Digital Files


Overview of Part FiveTh

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Part Five:

Working with Digital Files


1. Identify and explain the differences between bitmapped and vector images.2. Explain the different characteristics of grayscale and color bitmapped images.3. Explain and identify the characteristics of images at varying bit depth.4. Explain why fonts are able to be visually modified.5. Explain the difference between input and output resolutions.6. Explain the relationship of input resolution and file size.7. Calculate optimum resolution requirements for scanning.8. Explain the relationship between output resolution, lpi, and gray levels9. Explain the characteristics and uses of various image file types.

The digital revolution is upon us. Fromart and design to printing and publishing,the graphic arts world has been reducedto bits and bytes. We now live and work inor near cyberspace.

Prof. Frank. J. Romano

What does bitmapped mean? What is a vector? Is a “bezier curve” a baseball pitch? Why do weneed pixels? To rasterize or not to rasterize? What is resolution? Can you understand aninterpolated image? Do you know your file type? How do you pronounce “GIF”? Digital imagefiles require careful planning and production. You need to fully understand the variables inorder to produce optimum quality images for print and non-print media.


bitmapped pixelgrayscale bit depthbit bytevector object-orientedbezier curve rasterizedfont resolution input resolutionoutput resolution interpolationdownsizing downsamplingresolution rules gray levelsfile types compressionEPS EPS/DCSPICT TIFFJPEG PDFPhotoCD LZWGIF

Part Five: Working with Digital Files

1. Bitmapped images2. Grayscale and color

bitmapped images3. Bit depth4. Vector graphics5. Fonts are vector images6. Resolution7. Interpolation8. Resolution rules for

scanning9. Output resolution, lpi,

and gray levels10. File types

Part Five:Working With Digital Files


Bitmapped ImagesTh

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What is a Bitmapped Image?Bitmapped images are images that are made of picture elements (pixels) — tiny squares ofcolor. Images that you scan, photos that you make with a digital camera, and images thatyou make on the computer using paint or photo-realism applications are bitmapped images.

Bitmapped images are resolution dependent. If a bitmapped image has the correct image cap-ture resolution, and is prepared for the correct page layout size requirements, then the pixelsare not noticeable. If a bitmapped image has the image capture resolution too low, or isenlarged after being placed on the page layout, then the pixels can become very noticeable —this is sometimes a desired artistic effect.



Bitmapped ImagesTh

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What is Grayscale and Color Bitmapped Image?Grayscale bitmapped images are made of many thousands of pixels that are white, black, or inshades of grey. Color bitmapped images are made from thousands of pixels that are black,white, and many different colors.

Original computer-generated images, such as those made with the appli-cations “Painter” and “KPT Bryce3” (below), are also bitmapped images.

Did YouKnow?The size of abitmapped imageis often given intwo dimensions:actual pixel widthby pixel height.

An image that is3072x2048 pixelswill be 10.24”wide by 8.827”high when shownat 300 ppi andwill be 42.667”wide by 28.444”high when shownat 72 ppi.Theimage detail doesnot change.



Bitmapped ImagesTh

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What is Bit Depth?Bit depth is the number of bits used to record the information for onepixel of a displayed image. The greater the number of bits used, thegreater the number of different colors a pixel can have. Each pixel in abitmapped image is given a color value based on the bit depth of thefile.

An image with a bit depth of one has only two color values: solid colorand white. An image with two bits of information per pixel has fourpossible values (22 = 4). An image with eight bits per pixel can have 256(28) values of the same color, or 256 different colors (Index color). A 24-bit image has eight bits each for the red, blue, and green channels andyields 16.7+ million colors (256 x 256 x 256).

Did YouKnow?A bit (contractionfor BInary digiT) isthe smallest pieceof information in adigital system.A bitcan either be a “1”meaning “on” or a“0” meaning “off.”Eight bits equalsone byte.

2 Bit4 Colors

8 Bit256 (Index) Colors

1 Bit2 Colors

24 Bit16.7 Million

Colors

8 Bit256 Shades of Gray



Vector GraphicsTh

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What is a Vector Image?Vector images, also called object-oriented images, are made of mathematically defined lines(paths). Images made with applications such as Adobe Illustrator and Macromedia Freehandare vector images. Object-oriented applications store the image as a list of drawing instruc-tions that are complied from menu instructions and mouse movements.

A graphic image drawn in AdobeIllustrator is a vector image. Allof the detail in the image is madefrom individually drawn parts.The image file keeps track of eachitem in the drawing so you caneasily move, enlarge, or edit anypart of the drawing.

The vector paths can be made ofmany bézier curves, sort of likemathematical rubber bands thatcan be easily re-shaped to makea new outline for the object. Abézier curve has two end, oranchor, points (one serves as acontrol point) and a handlewhich shapes the curve.

Many bézier curves can belinked together without any dis-continuity to make a complexand smooth curved line.



Vector GraphicsTh

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You would oftenmake a vectordrawing in manyparts and layers.

A,B. You canremove the beefrom the rest ofthe picture. Youcan view theflower without thebee so you caneasily edit thedrawing. You canmanage objects asif each item weredrawn on separateclear layers.Objects can bemoved freely andcan be stacked andhidden by otherobjects withoutbeing erased.

C. Each part of avector drawing ismade of manylines. For exam-ple, you need todraw dozens oflines to make thedetails of the bee.

D. You can alsodraw the bee inmany separateparts.

E. You can makeeach section —such as the orangebee stripes — withmany smaller sec-tions that you canlock together as agroup.

A.

C.

E.

D.

B.



Vector GraphicsTh

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F. When youenlarge a vectorimage, you will beable to keep goodimage quality. Theprogram mathe-matically describesthe object to theprinter, which ren-ders the object atthe highest resolu-tion possible tothat printer.

G. You can colorthe lines andshapes of a vectordrawing. You caneasily change thecolors.

H. You canenlarge, reduce,rotate, reshape,and refill anyobject. The appli-cation programwill redraw theobject without anyloss of quality.

F.

G.

H.

Did You Know?When a vector image is dis-played on a monitor, it hasbeen rasterized.The monitor isa raster device and the imageis converted to bitmap pixelsfor display by the monitor’sRaster Image Processor (RIP).

Likewise, when a vector imageis printed or imaged onto filmor plates, the RIP converts thevectors to bitmap pixels.



FontsTh

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Fonts are Vector ImagesPostScript printer fonts and TrueType fonts are outline font formats that use vectors to createthe outlines of the font character. The font characters can be resized, scaled, angled, skewed,and rotated without any loss of quality. The program mathematically describes the font char-acter outline for the printer.

In the following example, the font “GillSans Bold Italic” is set at 36 pt. in each variation.

GillSans BI36 point

GillSans BI

36 point

GillSans BI

36 point

GillSans BI36 point

GillSans BI36 point

GillSans BI36 point

GillSans BI

36 point

Horizontal scale = 150%

Vertical scale = 150%

Normal

Skewed at 30°

Text angled and skewed at 30°

Text box rotated 10°

Text angled15°

Horizontalscale = 50%



ResolutionTh

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Unraveling the Mysteries of ResolutionThere seems to be no consistent use of the resolution and frequency digital imaging terms inbooks, articles, and even in product advertising. The terms dpi (dots), ppi (pixels), and spi(samples or spots) are often interchangeably used for input or output device resolution. Lpirefers only to halftone dot screen frequency. In effect, there are limited meanings: input(scanning) resolution, output (imaging/printing) resolution, and halftone screen frequency.

Input resolution - how much data is sampled; defined as samples-per-inch (spi) and pixels-per-inch (ppi) in most instances.

Output resolution - the absolute number of distinct points with which a system can rendera visible image: pixels-per-inch on a monitor, dots-per-inch on a digitally printed page.

Screen frequency - the number of lines or rows of dots per unit measure on a halftoneimage: lines-per-inch (lpi) or lines-per-centimeter (L/cm).

Resolution and File Size

The input resolution ofan image has a directrelationship on the filesize of the image. (fig. A)

The width and height ofan image can be definedin pixel dimensions.

Digital cameras and con-tinuous-tone filmrecorders most oftendefine image size in pixeldimensions.

Monitor resolutions arestated in pixel dimen-sions: 640 x 480, 832 x624, 1024 x 768

Kodak PhotoCD® andsome CD-ROM digitalimage files are stated inpixel dimensions (fig. B)

The pixel dimension vs.actual image reproduc-tion size is directly relat-ed to image resolution.(fig. C)

A

C

B

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ResolutionPart Five:Working With Digital Files

Increasing Input Resolution: InterpolationInterpolation is the algorithmic increase of image resolution by the addition of new pixelsthroughout the image, the colors of which are based on neighboring pixels, providing a high-er apparent resolution. Interpolation may be a function of the scanner software or may occurin image manipulation.

Interpolation cannot add more detail information to a scanned image. Detail is determined atthe time of the original scan or digital image capture. Interpolation can help smooth jaggededges in photos and line art when the image is enlarged because interpolation provides moredata points.

The original image resolution for thisRGB JPEG picture file was 170 ppi. Thepixel dimension of 340 x 508 made anon-compressed file size of 507K. Theprint image size is 2 x 2.988 inches.

The interpolated (resampled to be athigher resolution) image resolution forthis RGB JPEG picture file is 300 ppi.The pixel dimension of 600 x 896 made anon-compressed file size of 1.54MB. Theprint image size is still 2 x 2.988 inches.

The opposite procedure — when animage is resampled to result in a lowerimage resolution — is called eitherdownsizing or downsampling.

An image that undergoes repeated inter-polation and/or downsizing will likelyhave significant quality degradation.

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Resolution Rules

Resolution Rules for Scanning (based on Agfa publications)

The scan (input) resolution needed for any specific image depends on the percentage ofreproduction (original image size ÷ layout size), and the output method.

For Line Art:

Scan Res (R) = Output Device Res x % of reproduction (R = maximum of 1200 dpi)

examples:

Res = 600 dpi x 1.25 (125%) = 750 dpiRes = 600 dpi x 1.5 (150%) = 900 dpiRes = 1200 dpi x 1.5 (150%) = 1200 dpi (maximum needed)

For halftone output (e.g. film, CTP):

Input Resolution (R) = lpi x % of reproduction x QF (Quality Factor)

QF = 1.5 if lpi > 133 QF = 2 if lpi ≤ 133 (some advocate a QF of 3 if lpi ≤ 85)

examples:

Res = 133 lpi x .75 (75%) x 2 = 200 dpi (199.5)Res = 133 lpi x 1 (100%) x 2 = 266 dpiRes = 133 lpi x 1.5 (150%) x 2 = 400 dpi (399)Res = 200 lpi x .75 (75%) x 1.5 = 225 dpiRes = 200 lpi x 1 (100%) x 1.5 = 300 dpiRes = 150 lpi x 6.5 (650%) x 1.5 = 1500 dpi (1462.3)

For continuous tone output (e.g. ink jet, dye sub):

Input Resolution (R) = % of reproduction x Output Device Resolution

examples:

Res = .75 (75%) x 400 dpi = 300 dpi R = 1 (100%) x 400 dpi = 400 dpiRes = 3 (300%) x 400 dpi = 1200 dpi

For stochastic screening (FM)

Input resolution (R) = comparative lpi x % of reproduction

examples:

Res = 200 lpi x 1 (100%) = 200 dpiRes = 200 lpi x 1.5 (150%) = 300 dpiRes = 300 lpi x 1.5 (150%) = 450 dpi

Important note:

When a digital printer has a built-in scanner interface, the system software will calculate theneeded scan resolution based on percentage of reproduction and printer output resolution.

Most digital color printers have a “continuous tone” or “photographic” image rendering option.Rather than use conventional halftone screen ruling patterns, these digital printers use FMscreening. One should get information from the vendor regarding optimal image resolution.


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Inverse Rule ofPrintable Gray TonesThe number of pixels in each halftonecell determines the number of print-able gray tones or gray levels.

The formula for calculating the print-able gray tones is:number of gray tones = (dpi/lpi)2 + 1

At any given printer resolution, thereis an inverse relationship between thescreen frequency and the number ofprintable gray tones.

Increase the halftone lpi and the number of gray levels will decrease.Decrease the halftone lpi at the same printer resolution and the number of printable gray levels willincrease. Below about 1200 dpi, a digital printer cannot use conventional halftone screening and achieveboth smooth gray scale tone rendering and halftone dot rendering small enough to avoid detection at anormal viewing distance.


Output Res, lpi, & Gray LevelsThe printer/imagesetter output resolution, the halftone screen frequency, and the gray levels(printable gray tones) are all inter-dependent.

The higher the screen frequency, the fewer the levels of gray you can get at a given outputresolution. Reduce the screen frequency, or increase the output resolution, and you get moreprintable gray tones or gray levels. This is a critical concept in tone and color reproductionand in gradient blends.

The number of gray levels is determined by the number of dots (pixels) in a halftone cell. If acell is 8 x 8 (64 dots) there are 65 possible gray levels including white and black — all dotsoff and all dots on. A cell that is 16x16 yields 257 (256) gray levels.

Resolution & Gray LevelsPart Five:Working With Digital Files

Number of printable gray tones (gray levels) = (outputresolution dpi ÷ halftone lpi)2 + 1.

examples:

(2400 dpi ÷ 150 lpi)2 = 162 = 256 + 1 = 257 gray levels








A halftone cellbased on an 8 x 8pixel grid has 64total pixels. Eachadditional pixelimaged will increasethe percent dot areaby 1/64 or 1.5%.

A halftone cellbased on an 16 x 16pixel grid has 256total pixels. Eachadditional pixelimaged will increasethe percent dot areaby 1/256 or .03%.



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File Types: Alphabet SoupThere are many image and document file types. Photographic image files may be saved asPhotoshop, TIFF, EPS, PDF, JPEG, GIF, PICT, PhotoCD and more. Each application has anative file type. Files can be saved as PostScript and as Acrobat PDF.

What do these different file types mean? What is the need for, and impact of, all these filetypes? How do you choose the right file type for your specific need and situation?

File Types GlossaryEPS Encapsulated PostScript - A file format used to transfer PostScript image infor-

mation from one program and platform to another. The file includes PostScriptcode and a low res bitmapped representation of the image.

EPS/DCS EPS Desktop Color Separation - An image file format that creates five files foreach color image: one PostScript file for each CMYK channel and one preview file.

GIF Graphics Interchange Format - A standard developed by CompuServe for bitmapimages up to 256 colors and used for World Wide Web images, not for commer-cial printing.

JPEG Joint Photographic Experts Group - A set of standards developed by this group forcompressing and decompressing digitized still graphic images. JPEG is a lossycompression method. JPEG is widely used on the World Wide Web, but is not pre-ferred for use in professional commercial printing, since image quality is degrad-ed due to data loss. JPEG files require a compromise decision to determine levelof image quality and amount of file compression.

LZW Non-lossy compression method often used with TIFF files. With grayscale andcolor images, LZW usually yields about a 2:1 compression ratio.

PDF Portable Document Format - A PostScript-based streamlined file format devel-oped by Adobe for the transfer of pages across platforms and output strategies.

PhotoCD A proprietary image file format developed by Eastman Kodak for storing photo-graphic images in multiple resolutions on a CD. Images can be easily accessed foruse in professional printing.

PICT A common file format for defining bitmapped images on the Macintosh.

PostScript A page description language from Adobe that comprises software commands thatform the desired image on an output device when translated through a RIP.

TIFF Tagged Image File Format - A file format used to represent black-and-white,grayscale, and color bitmapped images, particularly those produced by a scanner.

TIFF/IT An ANSI- and ISO- accredited standard page file format that provides a high levelof file security (difficult to modify) and cross-platform portability.



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File Types and SizesDifferent file types yield widely different file sizes. The following list of files are all for thesame image that has the same resolution.

ID#

1

2

3

4

5

6

7

8

9

10

11

12

13

14

The image filesare listed inascending orderby file size.

The explanationof each file islisted below.

ID# Description

1 JPEG - Quality Low (1), Compression Highest

2 JPEG - Quality Low (3), Compression High

3 JPEG - Quality Medium (6), Compression Medium

4 EPS RGB file with medium JPEG compression selected in EPS dialog box

5 GIF export file

6. Photoshop PDF file

7. JPEG - Quality Maximum (10), Compression Minimum

8. TIFF (RGB) with LZW compression

9. Original PhotoCD image

10. Photoshop native file

11. PICT file

12. TIFF (RGB) without LZW compression

13. EPS (RGB)

14. EPS (CMYK)



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The EPS/DCS file formatcan only be used withCMYK color image files.

The DCS format allowseach high resolutioncolor channel to besaved separately andopened as needed foroutput to the PostScriptfilm, proof, or plateexposure system.

A Kodak PhotoCDimage file can beopened in five differ-ent pixel resolutions:

3072 x 20481536 x 1024768 x 512384 x 256192 x 128

Having five resolu-tions allows for abetter match of fileand image size andoutput requirements.

2048



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Lossless

With a lossless compression scheme no data is lost. Compression utilities, such as StuffIt,CompactPro, PKZIP, WinZIP, and LZW, images or other types of data are copied in a way thatall original data is “shorthanded” to eliminate redundant segments of code. The resultingcompressed file size depends on the complexity of the data and can range anywhere from thesame size to a small fraction of the original.

Lossy

A lossy image file-compression scheme is one in which some of the color information isthrown away when an image is saved. The viewer typically is unaware that lossy compressionhas been performed on an original image file because the “lost” image data areas areextremely subtle, and mostly unimportant to the human eye. JPEG is a lossy compressionscheme.

File Compression

JPEG

JPEG (JPG) is a file format and a lossycompression scheme developed by theJoint Photographer’s Experts Group. Animage saved as JPEG retains most of theimage’s visual information, while com-pressing the file by from 5 to 100 timesthe size of the original file dependingon the file size vs. quality compromiselevel that you choose.

When saving an image to the JPEG for-mat you can choose from have severaldifferent formats: Baseline (‘Standard’),Baseline Optimized, and Progressive.Baseline Optimized retains more colorfidelity. Progressive produces a verysmall file that can be placed in a WorldWide Web page. Progressive JPEGimages open on the Web by showingsuccessively more detailed versionsuntil the maximum resolution of thefile is reached.

Repeated JPEG save-open-save at highcompression levels will quickly flattenan image resulting in noticeable detailloss as shown in the images at the left.

Part Six:Using Color Within Applications


Overview of Part SixTh

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Part Six:

Using Color Within Applications


1. Identify the characteristics and uses of application color pickers.2. Identify the characteristics and uses of solid and process colors.3. Explain the color printing capabilities of offset lithography and digital printing.4. Identify the components of the Pantone® color system.5. Explain the organization of the Trumatch® color system.6. Explain the importance of accurate color naming.

“White does not exist in nature.”

Pierre-Auguste Renoirartist

Why do we sometimes want more than merely CMYK? What is a “color picker”? What is a“spot” color? What is the difference between a solid color and a process color? What are fac-tors affecting your choices? Can a solid color really become a process color? Why are Hi-Ficolors called “Hi-Fi”? What are the features of Pantone® and Trumatch® process color speci-fication systems? How many different ink colors do we need and when do we need them?


Color picker

Color libraries

Pantone®

Trumatch®

Process color

Spot color

Solid color

High-fidelity color

Part Six: Using Color Within Applications

1. Color Pickers

2. Process vs. Solid Colors

3. High-Fidelity Color

4. Pantone®

5. Trumatch®

6. Color Naming



Color PickersTh

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Choosing Colors with a Color PickerWhen working on an image or page within a document, we often must select specific colorsfor text, fills, shades, and lines. These specific colors are defined and selected with similartools — perhaps with different terminology — within different applications. These colorselection tools are generally called color pickers.

There are two main factors that influence the way we work with color in our documents inorder to achieve our desired results: the application we are using and the final output device.

• Applications vary in the processes they provide for selecting colors and in the waythat they transmit color to the output device. Some applications work best with theRGB color model and others work with the CMYK model.

• The type of output you intend for the document —conventional printing, digitalprinting, monitor display — determines both the way you choose color as well asthe way you define the output/print settings. Some devices require CMYK, someRGB, and some handle both models.

When you select a color for a part of your image or page, you need to know the requirementsfor your specific job. This way you can plan for — and get — the best possible results.

RGBCMYK

Pantone

HSB

Spot color

TrumatchPostScript

QuickDraw

Process colorGDI



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The color pickerin the MicrosoftOffice suite ofapplications,enables you tochoose colorsusing RGB andHSB color mod-els. At the left isthe color pickerfrom MS Wordin Office ’98 forthe Macintosh.

Notice the ter-minology; thiscolor picker usesthe term“Luminance”rather than“Brightness”.

Choosing Color in Office ApplicationsMost digital printers must receive PostScript instructions to print an image or a document.Office applications, such as presentation, spreadsheet and word processing programs, do notcreate these PostScript instructions by themselves; they rely on the printer devices to createthem. To display and print, these applications use QuickDraw with the Macintosh operatingsystem and Graphics Device Interface (GDI) with the Windows operating system.

Office applications use the RGB color model for the color monitor display. They often includea palette with preselected colors. Some applications may allow you to add new colors to thepalette with a color picker.

With some office applications you are able to select colors base on hue, saturation, andbrightness, or even CMYK, but these applications always send RGB color data to the digitalprinter. An exception is when a CMYK EPS file is placed in a document; this images is send asCMYK data.

When working with the RGB color model for documents which are intended for print output,remember that the RGB color space (gamut) is different than the CMYK color space of theprinter. When you print the document, out-of-gamut RGB colors are converted to colors thatyour printing device can produce.



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Choosing Color in PostScript ApplicationsMost applications for pixel editing, illustration, and page layout can create the PostScriptinformation that they send to PostScript printers or save in PostScript files. AdobePhotoshop, Adobe Illustrator, Adobe PageMaker, QuarkXPress, and Macromedia FreeHand areall PostScript applications.

PostScript applications enable us to specify and work with color in a variety of ways: CYMK,named colors (Pantone®, Trumatch®), and, in some applications, RGB, HSB, or other colormodels and libraries. Below, the QuarkXPress 4.0 “Edit Color” dialog box lists the colormodels available in the color picker.

Generally, PostScript applications send color information to a printer as CMYK. With somecolor printers, RGB images may be placed in the page being printed; the printer’s RIP willmake the necessary RGB to CMYK conversions.

When you create and choose a color, remember that the displayed version will likely appeardifferent on different color printers. You can get software utilities which enable you to printcolor reference (swatch) sheets on each of the color printers in your facility. This enables youto select accurate colors. These reference pages should be printed on a color printer which hasbeen calibrated for optimized print quality.



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With many applications, the same color — or nearly the same — can be specified in morethan one color model. The two purples shown here are almost exactly the same when dis-played on a monitor. Are they the same in print — you be the judge.



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Some colors cannot be matched between RGB and CMYK color models. These colors are notcommon to both gamuts. “Green” is a good example. 100% green in the RGB color modeldoes not come close to matching green in the CMYK color model as made by 100% cyan and100% yellow.

Green RGB 100G

Green CMYK 100C + 100Y

When a RGB color model green is converted by QuarkXPress into CMYK green the result is acloser, but still does not match. 100% green (RGB) becomes a CMYK mix of 77.3%C, 0.4% M,100%Y, and 0.4%K. The magenta and black are negligible and probably would not print.

Things To Do...The best way to determine the exact colors printed by a specific printer is to simply print a referencefile. After the printer has been properly serviced to be in optimum condition, print a reference file ofcolor swatches.There are software utilities from Pantone® and Trumatch® as well as from RIPs such asFiery and Splash. By choosing colors from these reference charts, you can be sure of getting the sameresults from your printer.

Caution: the reference charts will likely not match the monitor display.To match the monitor and printoutput you need color management and calibration of the monitor to the output.



Process vs. Solid ColorsTh

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Process Colors (also called “Separated” colors)As learned in part two of this guide, the subtractive colors of cyan, magenta, yellow, withblack (CMYK) can be combined to make a seemingly limitless palette of colors. The amountof each process (CMYK) color is controlled by the percentage of area covered. We can omit aspecific CMYK color (0% = not used), or we may use a screen tint percent, or we may use asolid (100%) coverage. In fact, however, the CMYK process color model does not enable theprinting of all possible colors. Sometimes solid colors are needed for a design.

Solid Colors (also called “Spot” colors)A “solid” color is one that is printed with a single color of ink that has been blended to a spe-cific hue, saturation, and brightness. We may print a bright red ink, a deep burgundy red, apale red. We may print with orange ink, purple, brown, forest green, or metallic gold ink.These solid color inks may, of course, be printed at various percent dot area tint patterns inorder to achieve a multi-color effect with a single ink color.

Cyan = 45%

Purple Ink (simulated)

Magenta = 100%

Yellow = 27%

Black = 11%

Purple

A process color may require up to four inksand, therefore, must be on four plates. A solidcolor prints in a single color of ink from asingle plate.

When are Process and Solid Colors UsedProcess colors are used for printing color type and graphic shapes when:

• the job design already has process color separation photographs and/or illustrationssuch as in magazines and catalogs.

• the job design is being printed on a press or digital printer that is limited to CMYK.

Solid colors are used for printing color type and graphic shapes when:

• the job design has no process color separation photographs and/or illustrations

• the job design has process color separation photographs and/or illustrations but additional specific colors are desired for the text and graphic shapes, such as in package labeling and product brochures.

When solid colors arerendered in CMYK,some color matches areon target while otherscan be way off themark.

So, what is the solu-tion?

Color selections shouldbe made with the printmethod considered.

If the job will be printedwith a conventionalink-based printingmethod, then we needto be sure that all color

specification meet bothdesign and production needs.

If the job will be printed with a digital color (CMYK) printer, then all colors should be madeas separated colors. If you have a printed color reference file (see page 54), then colors can beselected from that print. Separated RGB and separated CMYK colors can be used, dependingon the specific document application and the digital printer.



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Solid-to-Process Color ConversionOften an illustration or a page has colors that are specified as “spot” or “solid” colors.Sometimes this is intentional — that is the color of ink that will be used for printing thatpart of the design. Sometimes, this is merely an error in the way that the color has beenspecified within the application; a separate ink color is not intended. The opposite is alsotrue. A color may be created and the specification as a spot or solid color may have beeninadvertently omitted.

So, what is the problem?

When printing the job with conventional ink-based printing systems, if a color is specified asa spot or solid color, then a separate printing film or plate will be imaged. Likewise, a colorthat is not designated as a spot color my really be intended as a separate ink color. In thiscase there would be a missing film or plate for the job.

However, in digital color printing almost all output is with CMYK toners or ink jet inks. Withdigital color printing, all colors — process and solid — are printed in CMYK. Solid colors arerendered in CMYK according to the color rendering software of the printer.



Hi-Fi ColorTh

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High-Fidelity ColorAs stated earlier in Part Two, the range of colors (gamut) of RGB and CMYK are both smallerthan the gamut of visible light and are slightly different from each other. A method ofincreasing the gamut for color printing is called high-fidelity (Hi-Fi). There are two very dif-ferent methods for printing Hi-Fi color:

• Pantone® Hexachrome™ - This method uses six colors: enhanced CMYK plus a special green and orange.

• maxCMY (also called CMYK,CMY and seven color Hi-Fi) - This method uses sevenplates: two each for CMY plus black. Where the photo has colors outside the normalgamut of CMYK, additional plates are used to print more CMY, as needed, on top ofthe first printing of those colors. The double printing provides for increased colorsaturation in the same way colors are deeper when we put a second coat of paint ona wall. Since the additional CMY dots are printed on solid areas the same dot anglesand screen frequency are used.

DuPont recently has discontinued marketing its Hi-Fi color product, HyperColor, which usedthe maxCMY seven-color model. Pantone® Hexachrome as the dominant Hi-Fi model.

Scanner RGB

Monitor RGB

Offset CMYK

Offset Hi-Fidelity

Using Hi-Fi Hi-fi printed pages oftenlook quite different fromCMYK pages, promptingits use for the impact of adifferent appearance.

Hi-fi printing is used inpackaging and catalogsfor improved productcolor matching.

Hi-fi printing can replacethe need for 10-12 colorsfor packaging and labels.



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The Pantone SystemPantone® is a company that makes a widely-used system of color specification. This system isused by virtually every designer and printer and components are licensed into all PostScriptillustration, pixel-editing, and page layout applications.

Pantone® does not make ink. Pantone® specifies colors, in solid ink colors as well as processcolors, RGB Web-safe colors, and high-fidelity colors.

A key point to always remember is that the selection guides are exactly that — guides. Wewill not be printing with the exact same presses, inks, and on the same substrate so we cannever exactly match the colors in the guides. This is especially important when comparingink and toner printing systems.

A second point to remember is that the colors in the printed guides cannot be displayedexactly on an RGB monitor. We can come close with color management, but even then weneed to be aware of the potential differences.

Selected Pantone® system components

A

B

Formula Guide (A)This guide displays on both coated anduncoated papers, the approximately 1000solid ink colors in the main Pantone®library.

Fourteen basic ink colors, plus transpar-ent white and black, are used in thisguide. An ink supplier, or the printingcompany may be responsible for mixingthe ink color.

Some metallic and special colors areincluded in the Formula Guide.

Process guide (B)This guide displays on coated paper onlythe approximately 3000 colors specifiedwith CMYK tints.

Tints are specified in 5% and 10% incre-ments of CMYK.

The Process guide can be used for bothconventional ink printing and for digitalprinting.



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Selected Pantone® system components - continued

Solid to Process guide (C)This guide converts the Formula Guidecolors to process colors using a 26-steptint system. Tint values for each CMYKcolor are designated by the letters “A”through “Z” with the letter “O” designat-ed as zero percent and the letter “Z”meaning 100% of that color.

The history of this guide is important; itwas developed before digital prepress.Film screen tints for the 26-step systemwere used for analog platemaking in off-set lithography. Digital printing can easi-ly create values in more than 26 steps.

In software applications, such asQuarkXPress, when a solid ink color (forexample, PANTONE 285) is convertedwithin the document to a CMYK color,this is the method of conversion.

With many colors, the conversion doesnot make a match that is close to theoriginal color.

Pantone® also makes color swatch guides metal-lic ink colors (D), pastel ink colors (E), forHexachrome high-fidelity colors, and for textile colors, printed on cotton and paper.

The Pantone® system also includes a variety ofsoftware utilities, such as ColorDrive, OfficeColorAssistant, and Personal Color Calibrator to enablebetter color specification and print consistency.

The Pantone® system is more than and ink colorspecification system. While the Pantone® systemwas created for conventional prepress, and manyof the components are specifically for thatprocess, the growth of digital printing and non-print media have led to the development of prod-ucts for these markets.

C

E

D



Pantone®Th

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Pantone HexachromePantone® Hexachrome builds upon a known color printing concept; adding any two colorsto the CMYK process color printing system expands the color gamut by at least 20 percent.The Hexachrome ink set includes a vibrant green and orange with a new enhanced CMYK inkset that is purer than traditional CMYK ink sets.

As a result, Hexachrome can print all of the traditional CMYK colors plus 90 percent of thePantone solid colors. Hexachrome has a gamut that is larger than the RGB color gamut dis-played on a monitor.

Designers and printersmay use the Pantone®Hexachrome fan books forcoated and uncoatedpapers which show the2000+ colors in theHexachrome model.

The Solids in Hexachromefan books shows which ofthe Pantone® solids canbe printed in Hexachrome.

Pantone® HexImage™ isa plug-in for AdobePhotoshop which canmake six-colorHexachrome separationsfrom RGB, CMYK, orL*a*b* images for place-ment in page layout files.



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The Trumatch SystemThe Trumatch® color system focuses on the digital prepress procedures. Specifications areonly given for process color, none for solid colors. Two swatch books are available, one forcoated paper and one for uncoated paper. Software utilities for printing color reference chartsare also available.

The pages on the Trumatch® swatch book, and the columns in the dialog box are organizedby hue, saturation, and brightness characteristics.

Depending on the software application you are using, you need to verify the “process” colorversus “spot” color designation. Some application color pickers may not clear or retain theselection, as needed, when the color model designation is changed.

The Pantone® Process and Trumatch® color libraries are correctly used as “process colors”.The Pantone® Coated and Uncoated color libraries are correctly used as “spot” colors.



Color NamingTh

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Color NamingNames for colors are added to a page layout document file in three ways:

• The Pantone® and Trumatch® color systems provide “named colors”.

• Custom colors are often given custom color names.

• When colors are used in vector illustrations and special effect image files (such as aduotone), the names for the colors used in these images are imported with theimages into page layout files.

Problems arise when one or more of the following situations happen:

• Two or more color names are given to the same ink color, such as “cyan” and“process cyan”. In this case the film or plate separations will likely have multiplecyan plates.

• Custom color names are used such as “orange bee stripes” which may be the samecolor as “Pantone S 18-1”. This can result in inconsistent color rendering.

• Colors intended to be process colors are specified as solids, and vice versa. This canresult in an incorrect number of printing plates.

Custom color names oftendo not provide any clue totheir actual constructionand specification.

A color may be a a separatedCMYK color, a separatedRGB color, or a spot color ineither CMYK or RGB. Thecolor “army green” at left isspecified as a spot colordespite the CMYK construc-tion. This will be output as aseparate film or plate.

Pantone® and Trumatch®have name codes whichidentify their constructionas spot or process colors.However, these names canbe misleading if someonehas incorrectly selected orleft unselected the “spotcolor” designation.



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A complex job with many pages and illustrations may have adocument-based colors palette that could seem excessive. Ifthey are all used and specified properly, then there is little or noproblem with a lengthy color list.

An easy way to verify that the color specifications match the jobrequirements is to view applications print specifications dialogbox and compare the number of separate plates listed, as in thisexample, with the job requirements. How many colors of inkwill be needed for that job?

This color naming problemis not an issue when print-ing to a CMYK digital colorprinting system; there areno separated plate colorsand no spot color inks.

This image of a lovebird was prepared as a duotone in AdobePhotoshop. The duotone ink colors were defined as black andPantone Process Cyan CV, a standard color name in the PantoneCoated library. The color “Pantone Process Cyan CV” is carriedwith the EPS image file when it is placed in a QuarkXPress page.

QuarkXPress will see “Pantone Process Cyan CV” as a different andseparate color than “Process Cyan”.

Part Seven:Color Management


Overview of Part SevenTh

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Part Seven:

Color Management


1. Identify the components in a color printing workflow.2. Identify key causes of color mismatch in print production3. Explain the role of the ICC (International Color Consortium) in developing color

management solutions.4. Explain the key components in a color management system.

“The rude awakening came afterthe printing was done. The colorshad been much more brilliant onthe original. Even on-screen, every-thing had looked a lot better.”

“PrintProcess” publication

Why is color printing so difficult? What causes the problems? When did “color management”get started? Can color ever really be “managed”?

Consistent use of color standards will help prevent misunderstandings and mistakes in theprint production process. In this part you will learn the key issues in color management andthe solutions that are being developed.


ANSI Color managementCGATS module (CMM)IT8 Perceptive mappingReference target Absolute colorimetricProfile mappingCharacterization Relative colorimetricColor rendering mappingColor Management Saturation mapping

System (CMS)DensitometerSpectrophotometerColorimeterTristimulus

Part Seven: Color Management

1. Need for Standards2. Need for Color

Management3. Color Predictability4. Tools for Color

Management5. Color Mapping6. Device Profiles7. Color Management

Modules



StandardsTh

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The Need for StandardsPrior to the mid 1980’s, the standards movement in graphic arts was almost non-existentexcept for ANSI (American National Standards Institute) safety, typography and the photo-graphic industry standards for film density measurement and color viewing conditions.

The Digital Data Exchange Standards (DDES) group, formed by vendors of color electronicprepress systems, recognized significant problems with the mix-and-match world faced byprinters at that time; color scanning, display, proofing, and printing were inconsistent andwithout standards. This led to the formation, and ANSI accreditation, of the IT.8 committee,which, in turn, led to the formation of CGATS. ANSI does not create standards, which in theU.S. are voluntary. ANSI accredited industry groups create the standards. Two graphic artsgroups are:

• Image Technology Committee #8 (IT8), formed in 1987, concerns itself with theexchange of digital data between color electronic systems and peripherals; since1994, a ;subworking group of CGATS. Three IT8 color reference targets were estab-lished as standards in 1993.

• The Committee for Graphic Arts Technology Standards (CGATS), established 1989.This group acts as an umbrella group to assist with graphic arts standards.

The IT8 7.1 is used tomeasure the values oftransmissive colorbeing read by a scan-ner or other inputdevice.

On the IT8 7.1 trans-missive color refer-ence target are colorpatches in six cate-gories:

• shadows

• middletones

• highlights

• CMYK colors

• RGB colors

• skin tones andfrequently occur-ring colors



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The IT8 7.2 is used tomeasure the values ofreflection color beingread by a scanner orother input device.

On the IT8 7.2 reflec-tion color referencetarget are color patch-es in six categories:

• shadows

• middletones

• highlights

• CMYK colors

• RGB colors

• skin tones andfrequently occur-ring colors

The IT8 7.3 is a digi-tal file of input datafor characterizationof four-color processprinting.

On the IT8 7.3 digitalreference target arecolor patches ineight categories:

• shadows

• high total ink

• saturated colorwith no black

• saturated colorwith 20% black

• CMY solid colors

• CMYK dot gain

• CMYK neutralgray balance

• frequent colors



Color ManagementTh

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The Need for Color ManagementEven with established standards, color is not easy to print and display consistently. The work-flow process begins with image capture. continues through rendering the image on-screen,and output by digital proofing, digital printing, and preparation of plates for color printing.All these systems function well independently, but color and visual perception are not pre-cisely controlled. Without color management, the components of the color printing repro-duction process do not match.

Each device in the imagingworkflow relies on a differentmethod to process colors.The technology utilized byeach device limits the rangeof colors (gamut) captured ordisplayed.

The purpose of color manage-ment is to provide color con-sistency and predictabilitythroughout the entire work-flow. The color managementsystem (CMS) does this bycorrecting for the differencesin color introduced by eachdevice in the workflow.



Color PredictabilityTh

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Color PredictabilityThe differences in color space (gamut) often leads to misunderstanding and concern becausecolor may have unexpected and unpredictable results.

There are two primary reasons why good color predictability is difficult to achieve:

• The difference in color gamut among the various devices in the workflow. For example, a print on an ink-jet printer used for proofing cannot match the presssheet from an offset printing press.

• Deviations from the standard performance of any device in the workflow. For example, a specific digital printer may not perform to the output “standard” for thatmodel.

Color Management and Color PredictabilityColor management can remedy the problems and become the solution providing for colorconsistency and predictability.

• CMS manages device color space differences.

• CMS transforms RGB scan data for colors into the CIE color space.

• CMS can provide the final transform into the printer’s CMYK color space.

• CMS can convert CMYK data for one device color space into CMYK data for anotherdevice or print reproduction.

• CMS can develop a characterization profile for any particular device.

• CMS can be set to correct color by automatically factor device profiles.

The purpose of color management is to compensate for the lack of color consistency betweeninput and output devices. CMS provides color predictability which ensures that the color datais converted in a reproducible way.

What is Calibration? Why is it Needed?Calibration is the term for measuring and adjusting the performance of a device. Devices,such as scanners, monitors, and printers, need to be calibrated in order to achieve consistentcolor from day to day and from device to device.

We must recalibrate when the device’s performance expectation parameters change. Theseparameters can change simply over time as the device shifts from its normalized performance.Heat, as the device warms to normal operating temperatures, as well as environmentalchanges, such as humidity and ambient room temperature, may cause performance shifts.

Printer toners and inks may have slight differences; calibration helps to reestablish normal-ized performance when consumables are changed.



Color MeasurementTh

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Tools for Color MeasurementThe IT8 color reference targets cannot be evaluated by perception. Accurate color measure-ment is critical to the color management process. Three devices used for color measurementeach have different capabilities and purposes: densitometers, colorimeters, and spectropho-tometers. These devices are available to measure transmitive or reflective color devices, asappropriate. Devices are available to measure monitor color, printed color, and colors on filmemulsions.

A reflection densitometer measures thereflective color reference target and thecolor bar on the press sheet to monitorcolor print reproduction. The density ofsolid ink patches and the percent dot areaof a tint patch cannot be measured visual-ly. At best, one can make a good guess atpercent dot area. A densitometer is need-ed to accurately read ink densities andpercent dot area.

Spectrophotometers measures light at manypoints on the visual spectrum and formulatesthe color of various products such as plastic,paints, inks, ceramics, metals. With a spec-trophotometer, we can obtain the same typesof numerical data as with a colorimeter andalso get a spectral reflectance graph. With itshigh-precision sensor and the inclusion ofdata for variety of illuminant conditions, thespectrophotometer can provide higher accura-cy than a tristimulus colorimeter.

Colorimeters mea-sure light much likethe human eye doesusing tristimulusred, green, and bluereceptors.Colorimetersexpress colorsnumerically accord-ing to international

standards, using CIEcolor space models.

A colorimeter maybe used to measureprinted colors whereproduct's appearanceis critical for buyer'sacceptance.



Color MappingTh

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Color MappingThere are different methods for mapping colorsthat are used by color management systems.

Perceptive Mapping

In perceptive mapping, all or most of the colorsin the original color space are adjusted in a waythat maintains the relationships between thecolors. Since the human eye is more sensitive tocolor comparisons and relationships than torecognition of a specific wavelength, thismethod of color mapping preserves these rela-tionships. Most people will not be able to noticethat the colors in the image have been adjusted.

Absolute Colorimetric Mapping

In absolute colorimetric mapping, all of the col-ors in the source image which are outside thetarget gamut are lost. These out-of-gamut colorsare clipped on the gamut boundary. This map-ping method may result in an image that seemsnoticeably different than the original image.

Relative Colorimetric Mapping

In relative colorimetric mapping, all of the col-ors in the source image which are outside thetarget gamut are replaced with colors that areinside the target gamut, while preserving thehue and lightness of the original color.

Saturation Mapping

In saturation mapping, all of the colors in thesource image which are outside the targetgamut are scaled to the brightest saturation pos-sible. the hue remains the same, but the light-ness may change.

target gamut

source gamut

In perceptive mapping, the colors in theoriginal (source) gamut are rescaled tobe within the target device gamut.Colors already withing the target gamutare also moved in order to maintaincolor relationships.

In absolute colorimetric mapping, thecolors in the original (source) gamutwhich fall outside the target gamut arereplaced with colors along the targetgamut boundary.

target gamut

source gamut



Device ProfilingTh

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Device ProfilesThe first step in establishing and using a color management system is calibrating the inputdevice (scanner). Each scanner is different in how it recognizes color and may introducesmall color changes each time an image is scanned. When the calibration process is complete,the information about the device is called a profile. This calibration process is also calledcharacterization.

Making a ProfileCharacterization — defining a device profile — is not a complex procedure, but it doesrequire careful procedures. Here are the typical steps for making a profile for a scanner.

• The scanner must be allowed to warm to full operating temperature. The color con-sistency of the light source is dependent on the scanner being fully warmed up.

• The scanner settings must be calibrated to the manufacturer’s recommendations. Allsettings should be set for normal operating conditions.

• Scan a reference target (IT8 7.1 for transmission, IT8 7.2 for reflection). Turn offany settings for descreening, sharpness, or tone curve adjustment.

• Record and compare the color values to the values of the colors on the original target. The manufacturer of the IT8 target supplies the color value data with eachtarget.

• CMS software enables one to compare the scanned color data with the suppliedcolor data in order to create a profile of the device. When the CMS software has thedevice profile information, it will control any color shifts accordingly and yieldresults that correspond to the original. The device color profile is described in termsof the device-independent CIE color model, not RGB or CMYK.

• After the color profile is saved, perform some scan tests to verify that the profileyields desirable results.

Profiles for monitors and print output devices and presses complete the list of profiles neededin a complete color management system. A monitor’s color output is measured using a col-orimeter which attaches to the monitor and measures the actual colors. A profiles for eachprinter is necessary. In some situations, such as sheetfed offset printing, different profiles areneeded for variables such as substrate and ink sets.

There are pre-made profiles that are available from device manufacturers. These profiles aregeneric to a given model and often are valid and acceptable. However, these supplied profilesmay not match the performance of an individual unit.

CMS uses the device profiles to bring consistency and predictability to the color printingworkflow. Without CMS, color printing is haphazard guesswork.



CMM’sTh

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Color Management Modules Desktop computer operating systems now incorporate color management functions in theiroperating systems. Operating system-level color management provides applications, peripher-als, and operating system components with a common interface and file format for control-ling color and converting colors between devices. This approach to color management assistsin getting consistent color from different application on different output devices.

Color management modules (CMMs) convert color from one mode to another, such as RGBto CMYK, or one device’s CMYK to another device’s CMYK. CMMs are one of three compo-nents in OS-level color management, working with device profiles and a system level applica-tions programming interface. CMMs are third-party plug-ins for Apple's ColorSync on theMac OS, and available soon for Windows.

The CMM is a color translation engine (mathematical algorithm) that provides the interfacebetween the device profiles and the image files that need to be transformed between colorspaces. The CMM applies the data from both the source profile and the target profile to theimage.

The AppleColorSync controlpanel enables usersto select a preferredCMM or, by select-ing “Automatic,” letColorSync use theCMM specified ineach profile.

The CMYK setup inAdobe Photoshopenables selection ofcolor managementsettings for the printdevice profile, theengine (CMM), andthe rendering intentfor mapping out-of-gamut colors.

Part Eight:Digital Color Printing


Overview of Part EightTh

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Part Eight:

Digital Color Printing


1. Explain how xerography (electrostatic, electrophotography) printing and ink jetprinting technology work.

2. Describe the market forces which are driving the increase in digital color printing.

3. Explain the concept of variable data printing.4. Explain what is meant by “on-demand” printing.5. Compare the capabilities of competitive digital printing systems.

Color sells!anonymous

“Data in, printed sheets out” is the commonly accepted definition of digital printing.What arethe technologies used? What are the market forces? What is the importance of variable dataprinting? What is “on-demand” printing? What are the digital printing system choices?

Digital printing is forecast to grow rapidly over the next decade, taking work form conven-tional printing processes and creating new market opportunities.


electrophotography electrostaticxerography seleniumtoner ink jetdrop-on-demand continuous ink jetarray bubble jetpiezoelectric crystals nozzlerun length turnaround timevariable printing target marketingversionalization individualizationpersonalization print-on-demand

Part Eight: Digital Color Printing

1. What is electrophotography?

2. What is ink-jet printing?

3. Digital printing market

4. Defining run length

5. Variable printing

6. Print-on-demand

7. Competitive products

a. black & white

b. color

XerographyXerography (also called electrostatic printing and electrophotography) is a printing processwhich uses electrostatic forces to produce images on the paper or other substrate.

Xerography typically uses an aluminum drum coated with a layer of positively-charged sele-nium. Light passed through the document to be copied, reflected from its surface, or imagedby a diode or a laser light source reaches the selenium surface. Areas exposed by light losetheir charge and do not attract the negatively charged particles of toner which are sprayedonto the selenium surface and form an image of the document on the drum. A sheet of copypaper is passed close to the drum, and a positive electric charge under the sheet attracts thenegatively charged ink particles, resulting in the transfer of the image to the copy paper.Heat is then applied tofuse the toner particlesto the paper.

Later improvementshave made it possible toprint in full color andprint on both sides ofthe paper.

Digital copiers are nowreplacing opticalcopiers. Digitalcopier/printer/faxdevices are networked



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1. charge drumselenium surface

Re-imageabledrum

2. laser imagingphotoconductive surface

of selenium

3. toner is applied

paper

4. transfer toner by electrostaticcharge5. fuse toner with heat

6. clean

Did You Know?Chester F. Carlson (1906 - 1968),American physicist, was the inventor of xerography (dry writing).When working in the patent department of a New York electronics firm, Carlson was plagued by thedifficulty of getting copies of patent drawings and specifications. In 1934, he began to look for a quick,convenient way to copy line drawings and text. Since others were already working on photographic orchemical copying processes, he turned to electrostatics for a solution to the problem. Four years laterhe succeeded in making the first xerographic copy. Carlson obtained the first of many patents for thexerographic process in 1940 and for the next four years tried unsuccessfully to interest someone indeveloping and marketing his invention. More than 20 companies turned him down. Finally, in 1944, hepersuaded Battelle Memorial Institute, Columbus, Ohio, a nonprofit industrial research organization, toundertake developmental work. In 1947 a small firm in Rochester, N.Y., the Haloid Company (later theXerox Corporation), obtained the commercial rights to xerography, and 11 years later Xerox intro-duced its first office copier. Carlson's royalty rights and stock in Xerox Corporation made him a multi-millionaire.

Factoid: Xerographic machines for full color copying became available in the 1970s.



XerographyTh

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Xerography ProcessOne does not need to be a physicist tounderstand the principle of xerography.In fact, there are only two things thatone needs to remember:

• Like electrostatic charges repel• Opposite electrostatic charges

attract

Xerography takes advantage of these two principles via a device called a photoreceptor. Thephotoreceptor receives, processes, and transferes images using static electricity. There aretwo types of photoreceptors: belt and drum.

The photoreceptor is coated with a light sensitive semiconductive material such as selenium.If a strong static charge is applied to the surface (selenium), the charge remains there aslong as the surface is dark. When light strikes the photoreceptor, it becomes a conductorallowing the current to flow. the charge is then allowed to pass to the substrate.

+ ++ –

Six Steps in the Xerography ProcessThere are six simple steps in the xerography process:

❶ Charging - The photoreceptor is positively charged with static electricity by a high-voltage wire, called the charge corona

❷ Imaging/exposing - Either reflected light image (copier) or a laser light (printer) isused to create the latent (unseen) image on the photoreceptor selenium surface.Where light exposes the surface, the charge is dissipated. The unexposed surfaceretains the positive static electricity charge. This is the image that will print.

❸ Development - The positively charged latent image on the photoreceptor is exposedto negatively charged toner. The toner is supplied to the photoreceptor via a devel-oper unit which has mixed the toner with a developer made of fine grain plastic anda magnetic material. The latent image becomes a visible image on the photoreceptor.

❹ Transfer to substrate - The substrate is positioned in register between the photore-ceptor and another high-voltage corona which gives a positive charge on the paper.The positive charge on the paper attracts the negatively charged toner from the pho-toreceptor surface. A second corona removes the charge from the paper to allowseparation from the photoreceptor.

❺ Fusing - Heat and pressure are used to bond the toner to the substrate.

❻ Cleaning - the photoreceptor is cleared of any remaining toner.

In color xerography, steps 1-4 are repeated for each color before fusing. The four-color imageis built layer upon layer either directly onto the paper or (better and faster) onto an interme-diate belt for a single transfer of the full color image onto the substrate.



Ink JetTh

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Ink Jet PrintingInk jet printing processes produce color and density on a substrate by controlling the depositof tiny droplets of ink which form an image. Special coated papers are needed to result invibrant, saturated colors. There are two basic categories of ink jet printers: continuous ink jet– typical of high-speed production systems – and drop-on-demand ink jet – typical of desktopand short-run units.

Continuous ink jet is based on a simple principle: a thin stream of liquid ink can be brokenup into a steady stream of uniform-sized droplets when subjected to high frequency vibration.Modern continuous ink jet systems use piezoelectric crystals that produce hundreds of thou-sands individual droplets each second.

The stream of droplets is controlled and directed by a charging electrode which deflectsunwanted droplets into a catcher and returned to the ink reservoir. Undeflected droplets flyonto the moving substrate to form the image. Continuous array ink jet printers use one ormore arrays or groups of ink jet nozzles to achieve high printing speeds. A typical high speedarray has 240 nozzles per inch in a 4.25" array (1020 nozzles). Two adjacent arrays will coveran 8.5" page size. Special coated papers are needed to result in vibrant, saturated colors.

Desktop and short-run wide format ink jet printers use drop-on-demand ink-jet printing. Indrop-on-demand ink jet, droplets are only formed when needed for the page image. The twomost common ink-ejection mechanisms are bubble jet and piezoelectric crystal. Both causeejection of a tiny droplet from an ink chamber, which is immediately refilled from the inkreservoir to repeat the cycle as needed. Drop-on-demand is a relatively slow print technology.

ink reservoir

piezoelectric crystal

nozzleink

chamber

piezoelectric crystaldeforms

ink ejects andforms droplet

ink reservoir

heating plate

nozzleink

chamber

vaporized inkforms bubble

ink ejects andforms droplet

Two Drop-on-Demand ink jet types: piezoelectric crystal and bubble jet

Continuous ink jet

ink reservoir

deflector charge electrodes

return to ink tank

subs

trat

e

piezoelectric crystals



Digital Printing MarketTh

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Digital Printing MarketsThe digital printing market is focused on short to medium run length, with a rapidly growingemphasis on variable data printing.

Fixed Data/Images - Short to Medium Run – hybrid digital offset systemsVariable Data/Images - Short to Medium Run – b&w and color digital printing systemsVariable Data/Images - Long Run – ink jet; xerographic products in development

Economics of PrintingOffset printing has high initial (start-up) costs.Offset printing has a rapidly decreasing cost-per-page as the run length increases.

Digital printing has a nearly flat-line cost-per-page profile; cost of first copy is essentially thesame as the cost of 100th, 1000th, 5000th, etc.

What is the Print Customer Buying?Fast turnaround time (<2 days) Acceptable qualityCost advantages over offset (short run) No or minimal inventoryDocuments with value (less obsolescence) Variability or personalizationNOT merely buying technology

Faster Print Job Turnaround Times in FutureAt the end of 1995, 50% of all jobs were delivered within one week; by 2005, 80% of all jobswill be delivered within one week. (source: GATF, GAMA)

• Next day or sooner: 2% in 1995, 41% in 2005• In two days: 21% in 1995, 22% in 2005• Within one week: 28% in 1995, 24% in 2005• Within two weeks: 36% in 1995, 11% in 2005• Within one month: 7% in 1995, 1% in 2005• More than one month: 6% in 1995, 1% in 2005

print run lengthco

st p

er s

heet

low high

high offset

digital

Points to Ponder and Debate...What will be the market and technological hurdles to be solved to enable faster job turnaround?



Defining Run LengthTh

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Defining Print Run LengthPrint run length refers to the number of copies of the job that are printed in a single printsession. Usually the run length equals the total number of copies needed, including theamount of sheets needed for the projected spoilage in the printing, finishing, and bindingprocedures. The printing industry records a lot of data from many companies in order todetermine print run length patterns and projections. Paper making companies also use similar data to project the amounts of various papers that will be needed in the future.

Print Run Length Categories1 copy Ultra Short Run2-500 copies Very Short Run501-2,000 Short Run2,001-5,000 Moderate Short Run5,001-10,000 Moderate Run10,001-50,000 Average Run50,001-250,000 Moderate Long Run250,001-750,000 Long Run750,001-1,000,000+ Very Long Run

Market Share of Run Lengths1-500 copies 16.6% (of total market)500-2,000 33.5%2,001-5,000 22.3%5,001-10,000 13.8%10,000-100,000 5.6%>100,000 8.2%

Product Size and Run Length1-100 101-500 501-2000 2001-5000 over 5000

under 10 pgs 13% 14% 17% 9% 47%11-20 pgs 11% 9% 43% 19% 18%21-50 pgs 2% 11% 32% 29% 26%51-100 pgs 7% 12% 35% 17% 29%101-200 pgs 3% 9% 38% 29% 21%over 200 pgs 2% 6% 36% 31% 25%

Points to Ponder and Debate...What conclusions can you make from the above two data charts:“Market Share of Run Length” and“Product Size and Run Length”? What is the potential market share for digital printing? Is the digitalprinting market limited by product size?



Variable PrintingTh

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Variable PrintingVariable printing means that the individual pages can have different text and/or graphics.Variable information — from re-imageable image carriers — results in variable printing, thecritical component of customized printing. Offset lithography has a fixed image plate andcannot do variable printing – every press sheet in the run is the same as the others. Printingfrom fixed-image image carriers (e.g., offset plates) is called static printing

Variable printing itself has many variations: target marketing, variable versions, personalizedprinting, customized printing, and one-to-one marketing. The market for variable printingincludes direct marketing (don’t say “junk mail”), catalog marketing, and variable data print-ing from a database. Why is everyone interested in variable printing? Value added and highresponse rates!

Database PublishingDatabase publishing enables customized, personalized, and variable printing — a key marketinfluence on the growth of digital printing.

Often repeated quote: “The power of technology is in the hands of those who have the database.”

Target MarketingVersionalization: creating several versions tailored to the particular circumstances.Individualization: creating a unique product based on an in-depth database of known

characteristics (not always recognized as such by the end-user).Personalization: combines database and other marketing strategies to target specific

individuals.

Personalization Levels (level #12 has highest amount of personalization)

12. Every pixel is personalized11. Rules-based database and image merge, dynamic layout10. Database and image merge9. Hybrid documents (personalized with static printing)8. Database merge (link to all fields in database)7. Data merge (name, address, salutation, plus embedded in text)6. Document assembly (assembly pre-written paragraphs)5. Mail merge (name, address, salutation)4. Address merge (name and address on letter and mail piece)3. Name and address on mail piece; sorted by zip2. Addressed to "Resident"; sorted by zip, selected contents1. Addressed to "Resident"; same contents, every piece the same

Point to Ponder and Debate... Where does the data come from?



Print-On-DemandTh

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What is Print-On-Demand (POD)?The definition of Print-on-Demand (POD) or on-demand printing is usually based on its characteristics.

Print-on-Demand = short notice and quick turnaroundPrint-on-Demand = short, economical print runsPrint-on-Demand is today mostly associated with digital printingPrint-on-Demand definition may include binding and finishing operations needed to

complete the job in the short turnaround time required.

Who does Print-on-Demand?Any printing company or department can justify marketing and doing print-on-demand jobs.Commercial, book, and periodical printers, in-plant printers, quick printers and copy centers,prepress services, and even office superstores all may do on-demand printing.

What are the Benefits of Print-on-Demand• lower inventory costs• lower risk of obsolescent print materials• lower production and distribution costs

What is a Successful POD Business StrategySuccessful print-on-demand business strategies usually include marketing the entire process:

• Digital photography • Digital document development• Digital data transmission and storage• Digital proofing• Digital printing• Consultative sales — the printer as educator for the clients and designers• Market digital printing benefits, not merely converting offset to digital press jobs

Typical POD productsCustomized and non-customized

textbooksCustomized and non-customized

brochures, flyersCustomized and non-customized

catalogsCustomized and non-customized

couponsCustomized and non-customized

labelsAdvertising and direct mailProduct literature

Journal and magazine reprintsBooks, booklets, and manualsTechnical reports, documentation,

proposalsBound galleys of books for review

prior to print runsFormsNewslettersEnvelopesFinancial and legal reports and

documentsMenus, programsInvitations, letterheads, stationary

Signs, postersPresentation materials

Less-likely POD productsConsumer product packagingDaily newspapersMass-market booksTelephone booksLong-run general magazinesMass-distribution catalogsHigh-volume direct mailMass-market brochures, promo-

tional materials



Diverse Market NeedsTh

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Numerous Products for Diverse Digital Printing MarketsThere are several companies that manufacture digital printing products, and there are alsonumerous printer configurations and options for the business office graphics and the profes-sional graphic arts industry markets. Often, the same configuration will serve the needs ofboth markets. Customized configurations enable optimum cost, service, and performance.

Three broad categories of xerographic equipment include:• copiers (optical and digital, hardcopy scanner document input)• copier/printers (digital, hardcopy scanner and network document input)• printers (digital, network document input)

Each of these categories offer a wide range of devices from black & white to color, from low-to very high average monthly print volume requirements.

Home

Personal Publishers Creative Graphics

Office

In-Plant Printing Services

In-Plant Printing Services

Data Centers

Creative andProfessional

Services

Prepress andImaging Services

Commercial Printers

Quick Printers

Data CenterServices

Postpress andFullfillment Services

Office

Graphic ArtsIndustry

Other Industries andOrganizations

Photo

Color Market Segmentation

Vendors mayhave variousproducts that aretargeted for all orselected markets.

Various digitalfront-end (DFEs)and color man-agement solu-tions are avail-able, dependingon the vendor.

There are simplexand duplex print-ing and in-linefinishing options.

Digital color print systems range from 4 to100 pages per minute; from single-pagecut-sheet sizes to continuous web feed.

Prices range from desktop printers under$1500, to low-volume network printersabout $7000, to high-volume web printersat about $400,000.

Digital printersare used to pro-duce:

1. intermediateproofs for tradi-tional printprocesses.

2. final proofsfor digital print.

3. final printproduction out-put of short tomedium runlengths.



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Competitive Production Digital Printing ProductsThe number of companies which produce and markets digital production printers is large.There is an even greater number of systems, a number that is continually growing as newproduction digital printing systems are developed and introduced. One needs to continuallyreview the industry literature and company web sites to learn about current systems.

Here is a brief list of companies, and their web site URLs, that produce and market black &white and color production digital printing systems:

Xerox http://www.xerox.com/ digital black & white and colorIndigo http://www.indigonet.com/ digital colorAgfa http://www.agfahome.com/ digital colorXeikon http://www.xeikon.be digital colorOcé http://www.oce.com/ digital black & white and colorIBM http://www.printers.ibm.com/ digital black & white and colorHeidelberg http://www.heidelbergusa.com/ hybrid digital offsetScitex http://www.scitex.com/ ink-jetScitex/KBA http://www.karatpress.com/ hybrid digital offset

Xeikon, a company in Belgium, is the manufac-turer of web-fed digital color print engines mar-keted by four different companies: Xerox, Agfa,IBM, and, of course, Xeikon.

As of October, 1999, this print engine is consid-ered the top-of-the line color digital printer.

Growth of Color Digital Systems

1993 - NONE

First Xeikon and Indigo placements in 1994

First Xerox DocuColor 40 placements in1996; by 1998 the DC-40 placements totalmore than all others combined.

First Canon CLC-1000 placements in 1997

By 2005, projected to be 30,000 to 50,000 digital color systems placed worldwide.




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The Xerox DocuTech 135black & white digitalproduction printer hasenjoyed a dominant mar-ket share since its intro-duction. The DT 135 fea-tures digital and scannerinterface for acquiringcopy for production.

The Xerox DocuTech6180 black & whitedigital productionprinter increasedprint speed and pro-vided for additionalprinting substrateoptions.

The Xerox DocuColor40 features 2-upsheet-fed, 600 dpiprocess color printingat 40 ppm simplexand 30 ppm duplex.Copy can be receivedvia a network as wellas via the scannerinterface.




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The Xerox DocuColor 12, introduced in 1999,offers 600 x 600 dpi x 8 bit resolution, 12.5 ppmcolor and 50 ppm B&W at 8.5" x 11" sheet size;6 ppm/25 ppm with an 11" x 17" full bleed sheetsize capability.

A copier/printer, the DC 12 features a 400 x 400ppi scanner interface for hardcopy documentinput as well as network connectivity.

Intermediate Belt Technology (IBT) enables thefull-color image to be transferred to the paperin a single pass for faster production andimproved image quality over comparable units.

Optional sorter, choice of color controllers, andhigh-capacity feeder are available.

The Xerox DocuColor 4, introduced in 1999,offers 600 x 600 dpi x 8 bit resolution, 4 ppm

color and 16 ppm B&W at 8.5" x 11" sheet sizewith a 13" x 18" maximum sheet size.

A copier/printer, the DC 4CP features a 400 x400 ppi scanner interface for hardcopy docu-

ment input as well as network connectivity.

Also features the IBT for single pass full-colorprinting, optional sorter, choice of color con-

trollers, and high-capacity feeder.

The Canon copier and printer lines havemany units ranging from desktop inkjetprinters to this CLC1000, 31 ppm colorcopier/printer.




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Indigo produces several processcolor systems which use a “liquidink” toner, in digital offset pressconfiguration for sheet fed andweb fed production at 800 dpi.Some units also feature additionalspot color capability.

Many companies make wide-format ink jet printing systems.These ink jet systems are idealfor large size printing require-ments and are rapidly replacingthe traditional screen printingprocess for printing these typeof products.

Scitex is the dominant company inthe high-speed black & white inkjet printing system market.




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Scitex and KBA, in ajoint venture, producethe 74 Karat press tomeets the industry’sdemand for short andmedium run four-coloroffset quality printingwith a small floorspace footprint. The 74Karat is a hybrid digi-tal offset press thatuses direct-to-plateimaging and a self-cali-brating inking system.

The Heidelberg QuickmasterDI revolutionized the hybriddigital offset printing systemcategory. The QMDI was thefirst such system specificallydesigned and engineered fordirect imaging waterless off-set printing.

The Heidelberg Speedmaster74 DI four-up sheetfedpress, introduced in 1998,combines on-press thermalCTP with four and four-pluspress configurations.

Hybrid digital, direct imag-ing offset presses cannot dovariable printing.

A

A/D Conversion 37Absorption 14Advantages of added color 22

Color Captures Attention 23Color Enhances Productivity 24Color Improves Communications 23Color Sells 23

B

Bézier curve 51Bit depth 50Bitmapped images 48

C

CCD 35, 36Charge-Coupled Device 35Chester F. Carlson 88CIEColor Models 30CMMs 86CMYK 27, 37, 38, 41, 44, 46, 64, 70Color and Emotion 18Color Compression 20Color Conversion 70Color Management 79

Calibration 82, 85Color Predictability 82IT8 79, 80, 83Standards 79

Color Mapping 84Absolute colorimetric mapping 84Perceptive mapping 84Relative colorimetric mapping 84Saturation mapping 84

Color Models 25Additive color model 26

Color Triangles 29Color wheel 28, 29Subtractive color model 27

Color Naming 76Color Perception 15Color Picker 64Color reproduction 39Color Separation 33Color temperature 21Colorimeter 83Complementary colors 29Conventional Prepress 5

D

Densitometer 83Device Profiles 85

Characterization 85Digital Cameras 36, 37, 55Digital Color Printing 87, 96Digital File Output 7

Imposition 7PostScript Output Device 7Preflighting 7RIP 7Trapping 7

Digital Prepress 6Digital Printing Markets 91, 95Dot Gain 45Downsizing/Downsampling 56

E

Economics of Printing 91Electromagnetic radiation 12Electromagnetic Spectrum 12, 13Electrophotography 88Electrostatic printing 88


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EPS 59, 65EPS/DCS 59, 61

F

File Compression 62Lossless 62Lossy 62

File to Print Options 8Computer-to-digital printer 8Computer-to-film 8Computer-to-plate 8Computer-to-press 8

File types 59, 60Fonts 54

G

Gamut 30, 71, 81, 84GCR 46GIF 59Gray Levels 58Grayscale 49

H

Halftone 41, 44, 57Dot shape 41, 43Dot size 41, 42Screen Angle 41Screen frequency 41, 42, 55, 58

Heidelberg 100Hi-Fi Color 71

I

Indigo 99Ink Jet Printing 90

Continuous ink jet 90Drop-on-demand ink jet 90

Ink/Toner on Paper 40Interpolation 56

J

JPEG 59, 62

K

Kelvin Scale 21

L

Language of Color 16Brightness 16Color family 17Color shades 17, 29Hue 16, 17Luminance 16Saturation 16

LZW 59

M

Munsell Color System 32

N

Newton, Isaac 13, 28

O

Object-oriented images 51Offset Lithography 9Optical dot gain 45

P

Pantone® 72Pantone® Hexachrome 74PDF 59PhotoCD 59, 61Photomultiplier Tube 34


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PICT 59Pixels 48, 49, 55, 56PostScript 43, 54, 59, 65, 66Primary Colors 28Print Run Length 92Print-On-Demand 94Printing processes 9Digital 9Flexography 9Gravure 9Offset Lithography 9Process Color 38, 69Project Planning 2

GRACoL 2Project Questions 2

R

Reflection 14Resolution 48, 55, 56Resolution Rules 57Responses to Color 19

Emotional responses 19Physiological responses 19

Reverse engineering 4RGB 26, 37, 41, 64, 65

S

Scanners 34, 37Drum scanners 34Flatbed scanners 35

Scitex 99Secondary Colors 28Selenium 88Solid Colors 69Spectrophotometer 83Stochastic Screening 44, 57

T

Tertiary Colors 28The Human Eye 11TIFF 59TIFF/IT 59Timelines 8Turnaround time 2, 91TrueType 54Trumatch® 75

U

UCA 46UCR 46

V

Variable Printing 93Database Publishing 93Personalization Levels 93Target Marketing 93

Vector 51, 52, 53Visible light 12, 13

W

Wavelengths 12, 13, 14, 16White light 13, 14Workflow 4, 36Workflow Segments 4Workflow variables 4

X

Xerography 9, 88, 89Xerox 96Xerox DocuColor 12 98Xerox DocuColor 40 97Xerox DocuTech 135 97


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Understanding Color

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Transcript of Understanding Color