C Black-and-White Tone Targeting

| 73

C H A P T E R

| |Black-and-WhiteTone Targeting

OBJECTIVES

After completing this chapter you will be able to:

■ define and explain the purposes of tone targeting and tone correction.

■ describe and utilize the systems used to measure tones and tonal

range in photographs.

■ convert a measurement taken in one tone-measuring system to

another system’s measurement units.

■ use Photoshop’s tools to measure the tones and tonal range in a photograph.

■ explain the variables in printing processes that impact tone targeting.

■ use Photoshop’s tools to perform tone targeting.

■ use Photoshop’s tools to compensate for dot gain.

■ automate the tone targeting process using the Actions palette.

■ improve poor originals through the use of tone targeting.

■ perform tone targeting and correction on an image to be reproduced

by a specified printing process.

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Although Photoshop has tremendous power to improve colorphotographs, the vast majority of printed photographs are still reproducedin black-and-white. Photoshop has several features that will allow youto vastly improve the appearance of printed black-and-white photographs.For example, using Photoshop you can make photographs appear lighteror darker and compensate for the changes that are caused by inherentattributes of varying printing processes. Tone refers to the darkness orlightness of areas within a black-and-white photograph. The process ofmaking photographs appear more pleasing by lightening or darkeningparticular tones is called tone correction; the process of compensatingfor changes that are caused by inherent attributes of varying printingprocesses is called tone targeting. Tone correction is covered in depth inChapters 5 through 9. This chapter deals only with black-and-white tonetargeting. The skills that you will learn in this chapter by targeting black-and-white photographs lay the foundation for the color targeting andcorrection activities you will perform later in this book.

An Introduction to Black-and-White Tone Targeting

Reproducing images involves a series of simulations (Figure 2.1).Consider a photograph of the Grand Canyon printed in a magazine. Aphotographer uses a camera and film to capture a representation of thecanyon—the image on the film is a simulation of the real scene. Next, aphoto processing lab develops the film and uses it to print the imageonto a sheet of photographic paper, called a photographic print. Theprint is a simulation of a simulation of the Grand Canyon. A scanneroperator then places the photographic print onto a scanner to create adigital file that represents the photograph. The digital file is a simulationof a simulation of a simulation of the Grand Canyon. The Photoshopoperator then makes changes to the digital file resulting in, you guessedit, a simulation of a simulation of a simulation of a simulation of theGrand Canyon. Finally, the completed file is output to make a simulationof a simulation of a simulation of a simulation of a simulation of theGrand Canyon. When the image is subsequently printed using a printingpress, several more simulations may occur. By this point, it is a wonderthat the picture even resembles the original scene!

■ tone correction

■ tone targeting

| | Black-and-White Tone Targeting | 75

Figure 2.1Simulating anoriginal scene

GrandCanyon

ItemCamera

FilmPhotoPrint

ScannerFile

EditedFile

ComputerOutput

PrintedSheet

RealThing

Level ofSimulation

FirstLevel

SecondLevel

ThirdLevel

FourthLevel

FifthLevel

SixthLevel

Effects of Simulation

Each of the steps outlined above can cause the image’s quality todeteriorate. For example, film itself cannot capture all the subtle variationsin tone in nature and also has built-in deficiencies that cause ugly patternscalled grain. In addition, making a photographic print from film providesan opportunity for dust and dirt to become part of the image. On thepositive side, the making of photographic prints also allows skilled andtalented photographic technicians to improve parts of the image. Scanners,especially low-end desktop scanners, cause image degradation, especiallyin the shadow areas. Laser printers and imagesetters may be incorrectlycalibrated and yield halftone dot sizes that do not match the values thatexist in the digital file. Finally, each printing process, in combinationwith the substrate, causes halftone dot sizes to fluctuate. Fortunately,Photoshop allows you to take all these variables into account and adjusta photograph so that, when printed, it more closely resembles the originalscene.

Unless an image is to be viewed only on-screen, the primary goal oftonal manipulation is to account for the various attributes of a particularreproduction process/ink/substrate combination using tone targeting. Asecondary goal is to improve the overall appearance of the photographusing tone correction.

Optical Density

An original scene may have an almost infinite tonal variation, fromvery white whites to very black blacks. Original black-and-whitephotographs are continuous tone images that have an infinite number oftones, but the film and photographic paper on which an image isreproduced can reproduce far fewer tones than exist in the original scene.

■ optical density(density)

■ densitometer

■ densitometricvalue

The relative darkness of a particular tone is called optical density orsimply density. The density of a given area is measured with a specialmeasuring device called a densitometer and is expressed usingdensitometric values. Densitometric values are logarithms and, in printingand publishing applications, range from about 0.00 to 2.00 (for ink on

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paper). A detailed explanation of the mathematics used to calculatedensitometric values is beyond the scope of this book. However, youshould know that values close to zero are very white areas and valuesclose to 2.00 are very black. In fact, an area that has a densitometricvalue of 0.00 reflects all the light that strikes it and is not black at all. Anarea that has a densitometric value of 2.00 reflects only one percent ofthe light that strikes it and is very black.

■ highlightdensity

■ shadowdensity

There are two particular densitometric readings that are veryimportant to tone targeting—the highlight density and the shadow density.The highlight density is the densitometric value of the lightest spot in aphotograph—it has the lowest densitometric value to be found anywherein the photograph. The shadow density is the darkest spot—it has thehighest densitometric value to be found in the photograph.

■ tonal range

■ flat photograph

■ contrastyphotograph

If you subtract the highlight density from the shadow density, theresult is the tonal range. The tonal range is the range of tones—fromhigh to low—that an image possesses. A normal photograph usually hasa tonal range from about 1.60 to 1.80. If the tonal range is less than1.60, the photograph does not contain much contrast and can beconsidered flat. If the tonal range is above 1.80, the photograph iscontrasty and contains tones that are too dark. Very dark tones may beimpossible to reproduce on a printing press. Even though the tonal rangemay be normal, a photograph may still appear either too light or toodark depending on where the tones in the photograph are clustered. Iftoo many tones are dark, the entire photograph will appear dark.

Calculating the Gamma Ratio

White paper and black ink are customarily used to print areproduction of a black-and-white photograph. A typical white papermay have a densitometric value of about 0.10, and a solid layer of blackink may measure about 1.60. Therefore, the printing process using thispaper and ink combination would be able to reproduce a tonal range of1.50 (1.60 to 0.10) or less. If the original photograph has a tonal rangeof 1.95 and the press can only reproduce a tonal range of 1.50, the rangeof tones in the printed reproduction will be compressed by at least 0.45.This means that about one-fourth of the tonal range of the originalphotograph cannot be adequately reproduced using this ink and substratecombination.


Changing the ink and substrate for a given photograph will changethe reproduction’s tonal range. Using less-dense black ink or a less-whitesubstrate will decrease the reproduction’s tonal range while using blackerink and a whiter substrate will increase the tonal range. Use of a coloredsubstrate or colored ink will also decrease the tonal range of a halftonereproduction.

■ gamma ratio The ratio of the tonal range of an original photograph to the tonalrange of the reproduction is called the gamma ratio. The formula forcalculating the gamma ratio is:

gamma ratio = tonal range of originaltonal range of reproduction

If the tonal range of the original is 1.60 and the tonal range of thereproduction is 1.60, the gamma ratio would be 1.00. In such a case, everytone in the original would be reproduced with a matching tone in thereproduction. However, if the original has a tonal range of 2.00 and thereproduction has a tonal range of 1.50, the gamma ratio would be 1.33.


2.001.50

1.33

=

=

The higher the gamma ratio number, the flatter the reproduction.The lower the gamma ratio number, the more contrasty the reproduction.

Gamma ratio can be plotted on a graph called a gamma curve, withthe tonal range of the original shown on the x-axis and the tonal rangeof the reproduction shown on the y-axis. Figure 2.2a illustrates a 1.0gamma curve. Notice it is a 45-degree line. In a gamma curve of 1.0,every tone of the original would be reproduced with the same tone onthe printed substrate. A 1.0 gamma curve can only occur if the printedreproduction has the same tonal range as the original. For example, ifboth the photograph and printed reproduction have a tonal range of1.50, a 1.0 gamma curve could be used.

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Figure 2.2Comparison of 1.00and 1.33 gammacurves

2.00

1.67

1.33

1.00

0.67

0.33

0.00

0.33

0.67

1.00

1.33

1.67

2.00

Tonal range of original

Figure 2.2a: 1.00 gamma curve

Tona

l ran

ge o

f re

prod

uctio

n

2.00

1.67

1.33

1.00

0.67

0.33

0.00

0.33

0.67

1.00

1.33

1.67

2.00

Tonal range of original

Figure 2.2b: 1.33 gamma curve

Tona

l ran

ge o

f re

prod

uctio

n

■ gamma Figure 2.2b illustrates the 1.33 gamma ratio calculated for theprevious example. Notice that the curve in Figure 2.2b is flatter (not assteep) compared to the curve in Figure 2.2a. Flatter curves cause flatterreproductions. The 1.33 gamma curve will reproduce almost every tonelighter than it appears on the original. As you can see in Figure 2.2b, anarea on the original that has a densitometric value of 1.00 will bereproduced using a value of approximately 0.70, while a 1.33 area onthe original will be reproduced at 1.00.

NOTE

The term gamma is usedin several ways in thisbook. You have alreadyseen the term used asthe ratio of the tonalrange of an originalphotograph to thetonal range of thereproduction. Gammais also the name of aMacintosh Control Panelthat is used to adjustthe balance of yourmonitor. Finally,gamma is used as thename for a control,called the Gamma slider,in the Levels dialog boxthat you will use laterin this chapter. In allcases, gamma refersto a change in thecontrast in a repro-duction compared tothe original.

The gamma curve can be adjusted to match the tonal range of theoriginal and the tonal range of the reproduction process by using settingsincluded in most desktop scanner programs. Many desktop scanneroperating programs commonly use a default gamma of 1.8. This gammais too high for many photographs and tends to flatten them too much. Ifyou have a densitometer to read the tonal range of an original photographand if you know the tonal range that the reproduction process is capableof achieving, you can preset the gamma before scanning.

The tonal range of the reproduction is completely dependent on theprinting process, substrate, and ink to be used. To obtain satisfactoryresults, you must always find out in advance, from your print provider,the tonal range that will be possible given the unique combination ofthese three variables.

Exercise 2.1 Calculating the Gamma Ratio for a Given Original and Process/Sub-strate/Ink Combination

In this exercise, you will calculate the gamma ratio value to be enteredwhen scanning a black-and-white photograph. Assume that the originalhas a highlight density value of 0.15 and a shadow density of 1.98. Alsoassume that your print provider informed you that the printing process,


substrate, and ink that will be used to print the final reproduction canproduce a tonal range of 1.60.

1. Calculate the tonal range of the original:

tonal range = shadow density − highlight density

= 1.98 − 0.15

= 1.83

2. Calculate the gamma ratio: (the tonal range of the reproduction isgiven above)


1.831.60

1.14

=

=

3. You would enter a gamma ratio value of 1.14 (or as close as youcan) into the scanner software if you were scanning this particularphotograph. The gamma curve would measure 1.14 and would beflatter than a 45-degree line.

The Goal of Halftone Reproduction

To minimize the effects of tonal compression, a printed halftoneshould contain the lightest and darkest tones a process is capable ofproducing. This could be done by printing no dots at all in the highlightareas and printing a solid layer of ink in the shadows. However, unprintedand solid black areas in the middle of a halftone are painfully obvious.Figure 2.3 is a high-resolution unaltered version of the photograph youwill open in Exercise 2.3. Notice the solid white area between the girl’sshoulder and her hair and the solid black areas toward the bottom of herchin and on the right side of her face. These areas appear unsightly. Toprevent these unattractive too-white or too-black areas in a printedhalftone reproduction, the goal, when preparing most photographs forreproduction, is to position the smallest consistently printable dot in thehighlight density and the largest consistently printable dot in the shadowdensity. In other words, every part of a halftone should consist of dotsand every printable dot size should be used in most halftones.

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Figure 2.3

1

2

A high resolutionversion of theProject2.epsimage that containsunprinted and solidblack area

1. Too-light area(unprinted)

2. Too-dark area(solid black)

Exceptions to the Rule

■ specularhighlight

■ phantomhalftone

As in the case of every rule, there are exceptions to this goal. Thereare cases when a small area in a photograph is much whiter than the restof the image—for example, a reflection of a flash in a mirror. Thesesmall abnormally white areas are called specular highlights and can beprinted blank—that is, without any dots. Another exception would bewhen printing a very light photograph called a phantom halftone. Becausephantom halftones must be very light (sometimes type is superimposedover them), no large dots are used at all.

Using Densitometric Values

Densitometric values are one of the primary quality control systemsused by the printing and publishing industries. Densitometric values areused to measure original photographs, film that is imaged on imagesettersor cameras, and layers of printed ink. In fact, densitometric values areused in just about all phases of printing and publishing except inPhotoshop—unfortunately, the software engineers that developedPhotoshop decided against incorporating standard densitometric valuesinto its interface. Even though Photoshop does not use densitometricvalues, you need to become familiar with them because of their widespreaduse in controlling quality in the printing and publishing industries. Youcan use the Eyedropper tool and a Percent Dot Value to Density Valuetable to convert halftone dot values to corresponding densitometric values(Table 2.1).


Table 2.1 Percent Dot Value to Density Value

Percent dot value Density value Percent dot value Density value0 0.00 56 0.36

2 0.01 58 0.38

5 0.02 60 0.40

7 0.03 62 0.42

9 0.04 64 0.44

11 0.05 65 0.46

13 0.06 67 0.48

15 0.07 68 0.50

17 0.08 71 0.54

19 0.09 74 0.58

21 0.10 76 0.62

22 0.11 78 0.66

24 0.12 80 0.70

26 0.13 82 0.74

28 0.14 83 0.78

29 0.15 85 0.82

31 0.16 86 0.86

32 0.17 87 0.90

34 0.18 89 0.95

35 0.19 90 1.00

37 0.20 92 1.10

40 0.22 94 1.20

42 0.24 95 1.30

45 0.26 96 1.40

48 0.28 97 1.50

50 0.30 98 1.70

52 0.32 99 2.00

54 0.34

Relating Densitometric Values to Photoshop’s Tone Values

Instead of using densitometric values, Photoshop uses numbersranging from 0 to 255 to describe the value of tones. These values relateto the 256 shades of gray that PostScript is capable of producing. A zerovalue is black, while a value of 255 is pure white. If you ever need to

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convert a Photoshop tone value to a halftone dot value, use the followingformula:

halftone dot value = 1 − (

X )

255

when x = the Photoshop tone value. The halftone dot value can then beconverted to a densitometric value using Table 2.1.

Exercise 2.2 Converting a Photoshop Tone Value to a Densitometric Value

In this exercise, you will calculate the densitometric equivalent of aPhotoshop tone value.

Assume a given pixel has a Photoshop tone value of 64. Calculate itshalftone dot value and densitometric value.

1. Use the formula below, substitute 64 for x.


X )

255

2. Solve the equation as follows:


X )

255

1 − (

64 )

255=

1 − (.25)=

75%=

3. Use Table 2.1 to convert a 75% halftone dot value to a densitometricvalue.

Because there is no 75% halftone dot value shown in the table, usethe value that falls between the densitometric values of the 74%halftone dot value and the 76% halftone dot value. The result is adensitometric value of 0.60.


Exercise 2.3 Preparing the Photoshop Windows and Opening a Photograph

In this exercise, you will use the steps you learned in Chapter 1 toprepare the application and document windows then open a black-and-white photograph.

NOTE

If you are using yourown computer and havenot made any changessince you completedChapter 1 of this text,you do not need to doStep 1.

1. Turn on your computer. If you are working in a student laboratory,erase the Photoshop 4.0 Prefs from the Preferences folder within theSystem folder.

ÿ If you are working in a student laboratory, delete the Photos40.PSPfile in the Adobe/Photoshop/Prefs subdirectory using WindowsExplorer or Windows File Manager.

NOTE

Make all the changesto the applicationwindow described inExercise 1.2.

2. Launch Photoshop 4.0, then make any necessary adjustments to theapplication window so that it resembles Figure 1.8 on page 10.

3. From the File menu, choose Open.

4. Navigate to the Photoshop Student Files Folder, open theC2exercise.tiff (ÿ C2exer.tif) file, then click OK when the lockedfile message appears.

C2exercise.tiff opens in its own document window.

5. From the View menu, choose Show Rulers, or use the keyboardshortcut + .

6. On the Tool palette, select the Zoom tool.

7. Click the Options tab on the Navigator/Info/Options palette. Then,select the Resize Windows To Fit checkbox.

The Resize Windows To Fit option causes the document window toautomatically enlarge or reduce in size when the Zoom tool is usedto change the magnification of the image.

8. Move the Zoom pointer over the photograph, then click anywherewithin the image.

NOTE

If you were to close theNavigator/Info/Optionsand the Layer/Channels/Paths palettes beforeclicking the Zoompointer over the photo-graph, the windowwould increase in sizeso that the entire imagewould be displayed onthe screen.

The image is magnified to 200% and the document window enlargesto display more of the image. Note that the document window doesnot extend under the Navigator/Info/Options and Layers/Channels/Paths palettes (Figure 2.4). Therefore, your view of the image is notobstructed by palettes.

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Figure 2.4C2exercise enlargedto 200%

1. The window does notextend under theopen palettes.

1

Exercise 2.4 Measuring Densitometric Values

In this exercise, you will use the Eyedropper tool to measurePhotoshop’s halftone dot values and convert Photoshop’s halftone dotvalues to densitometric values.

1. If necessary, scroll so that the child’s face is visible in the documentwindow.

2. Click the Info tab on the Navigator/Info/Options palette.

3. From the Tool palette, select the Eyedropper tool. Then move thepointer around in the child’s face and notice the halftone dot valuesdisplayed in the Halftone Dot Percentage field in the Info palette.

4. Stop moving the Eyedropper pointer when its tip is over the highlighton the child’s nose at approximately the coordinates X: 2.771,Y: 1.333 (Figure 2.5).


Figure 2.5Area to measurewith the Eyedropperpointer

1. Measure the areashown at the tip ofthe Eyedropper tool.(XY coordinatesshown on Infopalette.)

1

NOTE

The location of theX and Y coordinatesof the Eyedropperpointer shown in thelower left corner ofthe Info palette werecaptured on a 17-inchmonitor with an800 × 600 monitorsetting.

5. Depending on where the point of the Eyedropper pointer is whenyou look at the Info palette, the Halftone Dot Percentage value mayread from 51% to 58%. If you stop in exactly the same place asshown in Figure 2.5, the Halftone Dot Percentage field will read53%.

6. Use Table 2.1 to convert a 53% halftone dot value to a densitometricvalue. You can see from the chart that this area has a densitometricvalue of 0.33.

Density Areas of Importance to Black-and-WhiteTone Targeting

■ highlights

■ midtones

■ shadows

When performing basic tone targeting in a black-and-whitephotograph, there are three areas that are important to consider. Theseare the highlight, midtone, and shadow areas of a photograph. Highlightsare the whitest areas of photographs, usually have densitometric readingsbetween 0.00 and 0.15, and are reproduced with halftone dots rangingfrom 0 to 29%. Midtones are the gray areas of a photograph. They havedensities ranging from approximately 0.16 to 0.50 and are usuallyreproduced with halftone dots ranging from 30 to 70%. Shadows arethe darkest areas of a photograph. These areas have densities above 0.50and are usually reproduced with dots that are larger than 70%.

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Exercise 2.5 Finding the Highlight and Shadow Densities of a Photograph andCalculating Tonal Range

In this exercise, you will use the Eyedropper tool to find the highlightand shadow densities of a photograph and calculate its tonal range. Youwill also save the image as an EPS file.

1. Make sure the Eyedropper tool is still selected, the magnification ofthe image is still 200%, and the image appears as shown in Figure 2.4.

2. Move the Eyedropper pointer around the image to measure thelightest and darkest areas of the photograph. Find the locations ofthe lowest halftone dot value and the highest halftone dot value.Write down the X and Y coordinates for each location.

You should find 0% and 98% halftone dot values in the areasindicated by the pointers on Figure 2.6. These are the highlight andshadow densities, respectively.

Figure 2.6Locations of thehighlight andshadow densities

1. The shadowdensity area

2. The highlightdensity area

1

2

3. Convert the halftone dot values to densitometric values. FromTable 2.1 on page 81, you will notice that a 0% halftone dot valuecorresponds to a 0.00 densitometric value and that a 98% halftonedot value corresponds to a 1.70 densitometric value.


4. Calculate the tonal range.

Tonal range = Shadow density – Highlight density

1.70 = 1.70 – 0.00

Because the value falls between 1.60 and 1.80, the tonal range isconsidered normal.

5. Return the magnification to 100%.

NOTE

You do not need to doStep 6 if you are savingon the hard drive orserver.

6. Insert your Photoshop Files 1 disk into the disk drive.

7. From the File menu, choose Save As.

8. Navigate until the name of your Photoshop Files 1 disk or folderappears at the top of the dialog box.

9. Save your file as Project2.eps on your disk using the Photoshop EPSformat.

10. When the EPS Format dialog box appears, do not select the IncludeHalftone Screen or Include Halftone Function options. Do not changeany of the defaults. Click OK to save the file to your disk.

Using a Histogram

Photoshop can show you a graphic representation of the tonal rangeof the photograph displayed on the screen. You can see this representationby choosing Histogram from the Image menu (see Figure 2.7).Unfortunately, it displays information about the photograph usingPhotoshop’s tone value system rather than easy-to-understand halftonedot values. The components of the Histogram window are explained inTable 2.2.

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Table 2.2 Elements of the Histogram window

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Exercise 2.6 Viewing and Interpreting a Histogram

In this exercise, you will use display and interpret a Histogram ofthe tonal values contained in the Project2.eps image.

1. From the Image menu, choose Histogram.

The Histogram window is displayed (Figure 2.7).


Figure 2.7The Histogramwindow for theProject2.eps file

1. Blended horizontalbar.

2. Histogram graph3. These fields are

only active whenthe pointer is placedover the histogramgraph.

4. A black-and-whitephoto contains onlyone channel—black.

1

2

3

4

2. Move the pointer anywhere in the bottom half of the window.

Notice the following information displayed in the window:

• The blended horizontal bar in the center of the window.

• Notice the shape of the histogram. It indicates that this is a verydark photograph because the majority of the pixels are on theleft side of the graph. Notice that there are some highlights, butvery few midtones. This photograph will not reproduce wellbecause too many tones fall on the left side of the graph.

• The Mean field indicates the average pixel has a Photoshop valueof 94.40. You can convert the mean Photoshop tone value tohalftone dot value and densitometric value using the formulaand Table 2.1 used previously. (The mean Photoshop tone valueof 94.40 corresponds to a halftone dot value of 62% and adensitometric value of 0.44.)

• The Std Dev field indicates that the standard deviation of thetones in this image is 81.64.

• The Median field indicates the median Photoshop tone value inthis image is 64. Using Table 2.1 and the formula found inExercise 2.2, this Photoshop tone value can be converted to ahalftone dot value of 75% and a densitometric value of 0.60.These values indicate that this is a very dark photograph becausehalftone values above 70% are shadows.

• The Pixels field indicates there are 59,040 pixels in the image.

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3. Move the pointer into the graph area. Notice that the fields on theright side of the window become active.

4. Move the pointer around within the graph. As you move the pointer,look at the Photoshop tone value in the Level field. Notice that thefarther you get to the left edge of the graph, the lower the Photoshoptone value displayed in the Level field. Notice also that the Photoshoptone values are higher toward the right side of the graph.

Remember that a Photoshop tone value of zero is black and aPhotoshop tone value of 255 is white.

5. Move the pointer until the Level field reads 84 (84 is equivalent to a67% halftone dot value and a 0.48 densitometric value). Notice theCount and Percentile fields.

• The Count field indicates how many pixels have a Photoshopvalue of 84 (there are 220).

• The Percentile field indicates the percentage of all the pixels inthe image that are 84 or darker. It means that 68.28% of all thepixels have a 67% or larger halftone dot value. Once again, thisindicates it is a very dark photograph.

6. Move the pointer until the Level field reads 5. Notice that there areno pixels with a level of 5 or less.

7. When you are finished looking at the Histogram, click OK.

Tone Targeting for Specific Printing Processes

Photoshop can be used to alter black-and-white images in two ways.First, it can be used to correct defective photographs—those that are toolight, too dark, or lacking in contrast. You will learn to improve theappearance of defective photographs in Chapters 5 through 7.

Photoshop can also be used to target particular halftone dot sizes tothe highlight, midtone, and shadow areas of the photograph. The choiceof a particular size of halftone dot to position in each area depends onthe combination of printing process and substrate that will be used toprint the photograph. Each printing process puts ink on substrates usingdifferent methods. The way the ink is printed impacts the size of theindividual halftone dots that can be reproduced. In Chapter 1, you learnedin Table 1.5 on page 54 that the printing process affects the lpi of the


screen that can be printed. In addition, the printing process influencesthe smallest and largest halftone dots that can be printed. For example,the gravure printing process is capable of printing smaller dots than screenprocess printing. The soft plates used in flexography cause halftone dotsto become enlarged, so smaller dots are specified for the highlights—theprinting process will then enlarge them to the appropriate size.

Each printing process has particular attributes that cause certaineffects. The attributes of a process are not faults—they are simply inherentin the particular process. It is ultimately the responsibility of thePhotoshop technician to take the attributes of the printing process intoaccount when performing tone targeting.

Other factors that affect the smallest and largest printable dots includelpi (very large or very small dots using high lpi screens are usually moredifficult to print), the ink (thinner inks tend to blot more into the papercausing it difficult to maintain very large dots), and the absorbency andsmoothness of the substrate (very small and very large dots on roughand on very absorbent surfaces are harder to print).

Fingerprinting

■ fingerprinting Ideally, each combination of printing press, ink, and substrate shouldbe fingerprinted. Fingerprinting refers to printing a series of tests todetermine the smallest and largest dots a particular press can produceusing a specified lpi on a particular substrate using a particular ink. Tofingerprint a press, prepare an image consisting of a series of differentsizes of halftone dots, similar to the illustration in Figure 1.13 on page20. The dots should include a range of sizes from about 2% to about98%. It is not necessary that each percent dot size be printed. However,a range of very small dots and very large dots should be represented.This series of halftone dots should be printed on each commoncombination of press, ink, and substrate typically used in a particularplant. The smallest and largest consistently attainable halftone dot sizesshould then be recorded. Well run professional printing businesses willhave this information available for use by Photoshop and other desktop/prepress operators.

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Because you probably do not have access to the fingerprinting datafor a variety of printing processes, Table 2.3 presents some rules of thumbthat reference books and/or professional printing businesses recommendfor the largest and smallest halftone dots that can be reproduced usingvarious processes and substrates. It is important that you understandthat the use of Table 2.3 for particular jobs is comparable to healingyourself by using a medical encyclopedia—unless someone who knowswhat he or she is doing runs some tests, you are just guessing!

Table 2.3 Examples of highlight and shadow dot sizes for variousprocesses and substrates

Process/Substrate/lpi Smallest Highlight Dot Largest Shadow DotOffset lithography/uncoated 10 90

Offset lithography/coated 2 95

Flexography/all substrates 3 85

Gravure/coated 3 98

Gravure/uncoated 5 90

Screen/50 to 65 lpi 3 95

Screen/85 lpi 5 92

Screen/150 lpi 20 87

Targeting Tones Using the Levels Dialog Box

Once you understand that the primary goal of tone targeting is toaccount for the various attributes of a particular process/ink/substratecombination, targeting tones in a black-and-white image is a fairlystraightforward task. In the next few exercises, you will use the knowledgeyou have gained so far to target tones in black-and-white photographs.

To target tones, you will use the Levels dialog box (see Figure 2.8).The Levels dialog box contains several elements that are summarized inTable 2.4.


Table 2.4 Elements of the Levels dialog box

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Using the Levels Sliders

You use the Input sliders in the Levels dialog box to increase theoverall contrast of an image and you use the Output sliders to decreasethe overall contrast of an image. You must understand what Photoshopis doing internally so that you can take full advantage of the tool.

Moving the Input sliders (black or white) in toward the center hasthe effect of increasing the overall contrast of the image. Why does thisincrease the contrast, you might ask? When you drag the black inputslider away from zero (its default position) to a higher level, Photoshopmaps all the pixels at that new level and lower (those to the left) to 0(black), and it stretches all the pixels with higher values to fill the entiretonal range from 0 to 255, thus creating more difference betweenadjacent pixels (increasing contrast). If you set the black input slider to20, then all pixels at levels 0 through 20 are mapped to level 0 andpixels above 20 are mapped to proportionately darker values (pixelspreviously at 25 might become 4, for example). This darkens the imageand increases the contrast in the shadows. Moving the Input whiteslider has the same effect at the opposite end of the tonal range. As youmove it away from 255 (its default position) to a lower level, Photoshopmaps all the pixels at that level and higher (those to the right of theslider) to level 255 (white), and stretches all the levels to the left of theslider to fill the entire tonal range from 0 to 255, thus creating moredifference between adjacent pixels (increasing contrast). If you set thewhite input slider to 233, then all pixels at levels 233 through 255 aremapped to level 255 and pixels at levels lower than 233 are mapped toproportionately lighter values (pixels previously at 228 might become248, for example). This lightens the image and increases the contrastin the highlights.

The gamma slider lets you adjust the midtones without affectingthe highlights or shadows, resulting in an image that is darker or lighteroverall. When you move the gamma slider, Photoshop moves the levelassociated with the midtone gray value (the fiftieth percentile). If youmove the gamma slider to the left (toward 0), the image gets lighter,because you are mapping a darker value to be the new midpoint (fiftiethpercentile). In effect, you are stretching the remaining pixels in theshadows to fill up the lower half of the tonal range, and you aresqueezing extra pixels into the upper half of the tonal range, where the


highlights are located. Conversely, if you move the gamma slider to theright (toward 255), the image gets darker because you are mapping alighter value to be the new midpoint (fiftieth percentile). The result isthat you stretch the remaining pixels in the highlights to fill up the upperhalf of the tonal range, and you squeeze extra pixels into the lower halfof the tonal range—the shadows.

The Output Levels controls let you flatten the tonal range of theimage so that you can target an image to the attributes of a specificprinting process/substrate combination. Decreasing the tonal rangedecreases the overall contrast in an image. How can that be? As youincrease the value of the black output slider, pixels with levels of 0 areremapped to the new level and pixels with higher levels are mapped toproportionately lighter values. If you move the black output slider to 20,then pixels with values of 0 are mapped to 20 and higher values aremapped to proportionately lighter values. This limits the darkest pixelsin the image to the level at which the slider is set. If you set the blackOutput Levels slider to 20, the distinction between the levels is maintained,but the pixels that were at level 0 go to level 20, those at level 1 go tolevel 21 and so on. As the tonal range gets decreased, contrast is decreased.The white Output slider behaves the same way as the black Output Levelsslider. If you set the slider to level 240, all the pixels at level 255 aremapped to 240, and so on.

Table 2.5 summarizes the use of the Levels input and output slidersto darken or lighten an image.

Table 2.5 Levels Adjustments with Input and Output Sliders

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96 | C H A P T E R T W O | |

the Auto button, which sets the highlight density to a zero percent halftonedot value and the shadow density to a 100% halftone dot value. Then,use the Output Levels field or sliders to match the appropriate highlightand shadow dot values for the correct printing process/substratecombination. If you use the Output Levels fields, you can quickly set thehighlight and shadow halftone dot values with the Photoshop tone valuesgiven in Table 2.6.

Table 2.6 Dot percent sizes and corresponding Output Levels values

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Exercise 2.7 Using the Levels Dialog Box to Adjust the Highlightand Shadow Dot Sizes

In this exercise, you will use the Levels dialog box to correct thehighlight and shadow dot sizes for the Project2.eps image. Assume thatyour instructions are to prepare this image for reproduction by offsetlithography on uncoated paper.

1. Make sure the Eyedropper tool is chosen.

2. From the Image menu, select Adjust, then choose Levels from thesubmenu. Alternatively, you can press + . The Levels dialogbox appears.

3. If necessary, drag the title bar of the Levels dialog box so that youcan see the highlight and shadow densities previously located anddisplayed in Figure 2.6.


When you are finished, the screen should look like Figure 2.8. Noticethe histogram, input and output sliders and fields, the buttons, andthe options. Table 2.4 provides an explanation of most of these items.

Figure 2.8

654 7

10

8

11

2

1

3

9

The Levelsdialog box

1. Histogram2. Input sliders3. Output sliders4. Decreases shadows5. Increases shadows6. Adjusts gamma7. Increases

highlights8. Decreases

highlights9. Auto density

button10. Output levels fields11. Input levels fields

4. Click the Preview option to select it.

NOTE

If Step 5 does not workas indicated, yourPreferences file is notset to the defaults. QuitPhotoshop and followExercise 1.1 on page 5.

5. Click the Auto button.

This causes Photoshop to place a 0% dot in the highlight densityand a 100% dot in the shadow density. Notice that the shadowinput slider moved to coincide with the left edge of the histogramand that the shadow Input Level field changed to a value of 6.

6. Determine the correct values for the highlight and shadow dot values.

First, consider the printing process and substrate combination—offsetlithography on uncoated paper. Then, use Table 2.3 on page 92 tolook up the proper highlight and shadow halftone dot sizes—10%and 90% respectively (please remember that Table 2.3 is only aguide—if you have real fingerprinting information available, use it).

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7. Move the Eyedropper pointer into the area beneath the child’s hairand above her shoulder—the highlight density previously identifiedin Figure 2.6. The Halftone Dot Percentage value in the Info paletteshould read 0.

Notice the change in the Info palette—the halftone dot fields haveexpanded to provide two columns of numbers. The left number refersto the old halftone dot value of the area at the tip of the Eyedropperpointer—as it was when you opened the Levels dialog box. The rightvalue indicates the new halftone dot value resulting from changesmade since the Levels dialog box was opened (Figure 2.9).

Figure 2.9The expandedInfo palette

1. Old halftonedot values

2. New halftonedot values

2

1

8. Use the mouse to move the White Output Slider to the left to darken(decrease) the highlights until the Highlights Output Level field readsabout 229.

9. Move the Eyedropper pointer into the highlight density area identifiedin Figure 2.6. Look at the Info palette. The Halftone Dot Percentagefield should read 0%/10%.

The field reading 0%/10% means that the highlight density that usedto measure 0% now measures 10%. The 10% reading matches thehighlight dot value required for offset lithography on uncoated paper.

10. Move the Black Output Slider a little bit to the right to lighten(decrease) the shadows. After you have moved the slider, move theEyedropper pointer into the shadow density area.

11. Move the Eyedropper pointer around in the shadow areas of thephotograph and look at the new halftone dot values on the Infopalette. You should see no new halftone dot value greater than 90%.If you do see a value above 90%, move the Black Output Slider


more to the right. If all the values are below 90%, move the BlackOutput Slider to the left. When you are done, the Output Levelsshadow field will read about 25 (Figure 2.10).

Figure 2.10The Levels dialogbox after thehighlight andshadow halftonedot values havebeen corrected

12. Click OK to accept the changes you have made to the image.

Look at the image. It probably looks light to you. This is good.Remember that the printing process will darken images!

13. From the File menu, choose Save to save your changes.

Dot Gain

■ dot gain Dot gain is a phenomenon that occurs in most printing processes.Dot gain causes halftone dots to print larger than they are supposed to.For example, suppose you specify a halftone dot size of 50%. The pressureused to transfer the ink to the substrate, coupled with the blotting actionof many papers, causes the dots to become enlarged. So, 50% dots canend up looking like 70% dots. Dot gain is not an error or flaw—it is anattribute of print reproduction. It does, however, make halftones lookdarker than they should. So, you must take dot gain into considerationwhen performing tone targeting. To see what happens when dot gain isnot considered, compare the midtones in Figure 2.3 on page 80 withthose in Figure 2.14 on page 104. Figure 2.3 illustrates how yourProject2.eps image would appear if dot gain were not considered. Anaccommodation for dot gain has been made in Figure 2.14.

Dot gain affects the midtones more than the highlights or shadows.The larger the circumference of the dot, the more likely it will be affectedby dot gain. However, very large dots start to overlap, so they do notgain too much. Tiny highlight dots are usually not greatly affected bydot gain either. Because of the considerable impact of dot gain onmidtones, dot gain is usually measured at the 50% dot. Using the same

100 | C H A P T E R T W O | |

sort of test that is used to fingerprint a press, a 50% dot’s size is measuredwith a densitometer or other dot-measuring device. The dot will usuallyread between 65 to 85%, a gain of 15 to 35%. Fifteen percent isconsidered acceptable dot gain, 20% is normal, and 35% is generallyconsidered unacceptable.

You should be aware that laser printers and office copy machinesreproduce images with a very high degree of dot gain. Many of thesemachines print images using powder crystals called toner rather than withink. Dots printed with toner generally appear larger than dots printedwith ink. In addition, higher lpi dots tend to gain more on laser printersthan lower lpi screens. For example, one tested 300 dpi laser printerproduced dot gain of about 19% when set to 35 lpi and 29% when set to53 lpi (which is the printer’s default lpi). The exaggerated amount of dotgain inherent in toner-based printing systems is the reason why the imageyou will print on a laser printer in Exercise 2.14 will look very dark.

The impact of dot gain is to darken the midtones without affectingeither the highlights or shadows very much. When performing tonetargeting, you must set the midtones to look much lighter than you wouldnormally expect. Dot gain will darken the midtones for you. You use theGamma Input Slider to adjust the gamma, or midtone contrast, of thephotograph (see Figure 2.9).

Exercise 2.8 Using the Levels Dialog Box to Compensate for Dot Gain

In this exercise, you will continue to target the Project2.eps imageby adjusting the Gamma slider in the Levels dialog box to compensatefor dot gain. Assume that the anticipated dot gain for the printing process/substrate combination is 20%.

1. From the Image menu, select Adjust, then choose Levels from thesubmenu. Alternatively, you can press + .

Notice how the histogram has changed to reflect the changes youpreviously made to the highlight and shadow density halftone dotvalues. In particular, notice that the White and Black Input Slidersappear outside the histogram. This indicates that the original tonalrange has been compressed to match the process/substratecharacteristics.


Figure 2.11 illustrates this tonal compression. The figure, which isnot visible on your monitor, was prepared by overlaying the contentsof the Levels dialog box as it appeared at the beginning of Exercise2.7 with the contents of the Levels dialog box now displayed onyour monitor. The black histogram represents the tonal range beforeit was compressed to match the characteristics of the printing process/substrate combination. The gray histogram represents the tonal rangeafter the highlight and shadow dots were targeted. Note that thegray tonal range is shorter than the black tonal range and that thegray tonal range provides neither as white whites nor as black blacksas the tonal range illustrated in black.

Figure 2.11

1

2

Tonal compressioncaused by matchingthe original tonalrange (black) to thecharacteristics ofthe process/substrate (gray)

1. Tonal range ofphotograph beforethe highlight andshadow halftone dotsizes were targeted.

2. Tonal range aftertargeting ofhighlight andshadows wascompleted.

2. Move the Eyedropper pointer around the image until you find anold halftone dot percentage value of about 70%.

The halftone dot value doesn’t need to be exactly 70%. Any dotbetween approximately 60% to 80% is acceptable. You will findseveral values in this range around the child’s eye. Write down the Xand Y coordinates for the location of the chosen halftone dot value.

3. After you have located an area with appropriate-sized dots, considerthe effect of dot gain.

Dot gain causes midtone dots to become enlarged. You have beeninstructed to plan on a dot gain of 20%, so a 50% dot will print asif it was a 70% dot. To compensate for this phenomenon, you must

102 | C H A P T E R T W O | |

decrease the size of a 70% dot until it measures 50%. When this50% dot is printed, dot gain will cause it to expand to 70. Thus, thetonal values of the image will be restored.

4. Move the Gamma Input Slider a bit to the left to lighten the midtones(see Figure 2.8 for the location of the Gamma Input Slider).

5. After you have made a gamma (midtone) adjustment, move theEyedropper pointer to the location of your chosen midtone dot. TheHalftone Dot Percentage value in the Info palette should indicate anew halftone dot value that is 20% less than the old halftone dotvalue.

6. If the new halftone dot value is between the old value and 20% lessthan the old value, move the Gamma Input Slider farther to the left.If the new halftone dot value is less than the old value minus 20%,move the Gamma Input Slider to the right.

You are finished when the old and new halftone dot values are 20%apart. For example, if you had a 69% halftone dot value, the newvalue should be 49% (Figure 2.12).

Figure 2.12Gamma adjustedin the Levelsdialog box

1. Location of areameasured

2. 20% differencebetween old andnew values

1 2


7. Click OK to accept your changes.

The image on the screen looks very flat and light. Do not worry.Remember that the printing process darkens images.

8. From the Image menu, choose Histogram. The Histogram windowappears (Figure 2.13).

Notice that many more pixels are now clustered around the middleof the histogram. Also notice the vertical white streaks that appearin the histogram. These streaks represent tonal values in which nopixels exist. To make the corrections you specified in the Levels dialogbox, the contrast between the midtones and the shadows wasincreased, leaving some Photoshop tone values unused. Finally, noticethe median Photoshop tone value—about 125. This value is abouthalfway between 0 and 255 and represents a big improvement overthe original distribution of tones (see Figure 2.7).

Figure 2.13

1

2

3The Histogramafter the highlights,shadows, andmidtones havebeen adjusted.

1. Pixels are moreclustered around thecenter compared toFigure 2.7.

2. The median fieldis 125.

3. Vertical whitestreaks indicateunused tone values.

9. Click OK to close the Histogram window (Figure 2.14). CompareFigure 2.14 to Figure 2.3 to see the improvement in the photograph.

104 | C H A P T E R T W O | |

Figure 2.14A high resolutionversion of theProject2.eps imageafter tone targetinghas been applied.

10. From the File menu, choose Save to save this image.

Using Basic Black-and-White Tone Targeting to Improve theAppearance of a Flat Photograph

Often, performing the necessary targeting procedures for a grayscaleor black-and-white image improves the overall appearance of aphotograph, thus eliminating the need to do any other corrections. InExercises 2.9 and 2.10, you will start with a very defective photograph—it is so light that you can barely see it—then use the Levels dialog box totarget the highlights, midtones, and shadows to compensate for dot gainand other press characteristics. This process will greatly improve theoverall appearance of the photograph as well as target its tones for printreproduction.

Exercise 2.9 Targeting a Very Flat Photograph for Flexographic Reproduction

In this exercise, you will open a very flat photograph, use the Levelsdialog box to improve the tonal distribution of the photograph, andtarget it for printing by flexography.

Assume that your instructions are to prepare this image forreproduction by flexography and that the common dot gain for thisprocess is 25%.

NOTE

Do not closeProject2.eps.

1. Open the file called C2exercise2.tiff (ÿ C2exer2.tif), found in thePhotoshop Student Files folder. Click OK when the locked filemessage appears.

Notice that the image is very flat and lacks contrast.


2. From the File menu, choose Save As. Navigate to your PhotoshopFiles 1 disk or folder. Name the file Project2b.eps, then save it as aPhotoshop EPS file. Accept all the default options in the EPS Formatdialog box.

3. From the Image menu, select Adjust, then choose Levels from thesubmenu.

The Levels dialog box appears.

4. Click Auto.

Photoshop automatically gives the highlight density a zero percenthalftone dot value and the shadow density a 100% halftone dotvalue, thus lengthening its tonal range. Notice the improvement inthe appearance of the photograph.

5. Consider the smallest and largest halftone dots that the printingprocess/substrate combination can produce. Use Table 2.3 on page92 to look up flexography (all substrates).

The minimum and maximum dot sizes are 2% and 80%, respectively.

6. Use Table 2.6 on page 96 to determine the Output Levels that willresult in 2% highlight and 80% shadow dots.

The corresponding levels are 250 and 51, respectively.

7. In the Shadow Output Levels field, type “51”; and in the HighlightOutput Levels field, type “250” (Figure 2.15).

The image changes to reflect your changes.

Figure 2.15The adjusted InputLevels and OutputLevels fields

106 | C H A P T E R T W O | |

NOTE

It is always best toaccept the changesto the highlight andshadow halftone dotvalues and then reopenthe Levels dialog box toadjust the midtones.Clicking OK to acceptthe changes causesthe tonal range andhistogram to be updatedto include the changesyou made to thehighlight and shadowhalftone dot values.It is easier and moreaccurate to adjust themidtones after the tonalrange has been updated.

8. Click OK to accept the changes to the highlight and shadow halftonedot values.

9. Open the Levels dialog box again.

Notice how the histogram has been stretched in comparison to thehistogram of the uncorrected image (compare it to the histogram inFigure 2.15).

10. Use the Gamma Input Slider to decrease the halftone dot values ofthe midtones (50 to 70%) by the specified dot gain value (25%).Use the same procedures you followed in steps 2 through 6 ofExercise 2.8.

When you are finished, the image on the screen will look very lightbecause of the large amount of dot gain inherent in the flexographicprinting process. When it is printed, the photograph will darkenappropriately.

11. When you are finished, click OK.

Exercise 2.10 Targeting a Very Flat Photograph for Offset Lithographic Printing

In this exercise, you will use the Levels dialog box to improve thetonal range of a photograph and prepare it for printing.

Assume that your instructions are to prepare this image forreproduction by offset lithography on coated paper and that the commondot gain for this process/substrate combination is 15%.

1. From the File menu, choose Revert. Click Revert when an alertappears.

The Revert command discards all changes that have been made sinceyou last saved and displays the last saved version on the screen.

2. Open the Levels dialog box.

3. Click Auto.

4. Use Tables 2.3 and 2.6 to determine the smallest highlight and largestshadow that this process/substrate combination can accommodateand the corresponding Output Levels.

5. Enter the values you found in Step 4 into the Output Levels fields.

6. Click OK to accept the changes you made to the highlight and shadowhalftone dot values.



8. Use the Gamma Input Slider to decrease the midtone halftone dotvalues by 15% (change a 65% dot to 50%). When you are finished,click OK.

Notice that the image on the screen does not appear as light as it didwhen you corrected the same image for reproduction by flexography.

The image appears darker on the screen because the process/substratecombination of offset lithography on coated paper can hold smallerdots and produces less dot gain than flexography.

10. From the File menu, choose Save to save your changes.

11. Close Project2b.eps.

Other Methods of Tone Targeting

In addition to the Levels dialog box, Photoshop provides severalother methods to target the tones of black-and-white photographs. Theseadditional methods can be found in the Adjust submenu of the Imagemenu (Figure 2.16) and include Auto Levels, Curves, Brightness/Contrast,and Variations.

Figure 2.16Other methods toadjust tones ofphotographs

Auto Levels Command

The Auto Levels command simply applies the same Auto functionthat is found in the Levels dialog box. It should not be used withouttargeting the highlight and shadow dot sizes using the Output Levelssliders or fields in the Levels dialog box.

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Curves Command

The Curves command is very important and useful and is covered indepth in Chapter 6.

Commands to Avoid

The Brightness/Contrast dialog box is deceptively simple and verydangerous. Adjusting the Brightness control simply shifts the tones upor down the scale. The Contrast control stretches the tonal range andthrows away information in both the highlight and shadow areas. Neitherthe Brightness control nor the Contrast control attempts to match theimage to the reproduction process/substrate combination. The use ofthese two controls is not recommended.

The Variations command is a very slick and extremely dangeroustool. It is designed for those who say “I’ll know what I want when I seeit.” It presents the current image along with a number of variations ofthat image—lighter, darker, and so on. However, it relies completely onthe accuracy of the monitor and does not attempt to match the image tothe reproduction process/substrate combination. Its use is notrecommended for print reproduction. It works fine, however, if you wishto correct an image that will only be viewed on a computer screen. Youwill use it for that purpose in Chapter 9.

A Start-to-Finish Checklist for Targeting Black-and-WhitePhotographs Using the Levels Dialog Box

This section serves as a review of the processes you should followwhen targeting a black-and-white photograph for print reproductionusing the Levels dialog box. Use this process on grayscale images afterthe lpi and image resolution have been set.


Table 2.7 A recommended process for performing tone targeting using the Levels dialog box

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110 | C H A P T E R T W O | |

Automating Tone Targeting Using the Actions Palette

Photoshop 4.0 allows you to automate repetitive tasks by recording aseries of actions you take to complete an operation. For example, in Exercises2.7 and 2.8, you followed a series of steps to target the highlight, midtone,and shadow dots. Assuming you have a number of photographs to correctthat are similar to each other and will be printed using the same printingprocess and substrate, you can record the actions you take to correct thefirst image, then play back those steps on additional images. You can alsoinstruct Photoshop to batch-process all the files in a given folder.

To access the Actions palette, open the Windows menu, then chooseShow Actions. The Actions palette appears on the right side of the screen.Its components are illustrated in Figure 2.17 and explained in Table 2.8.

Figure 2.17

67 5

1

2

3

10

89 4

The Actions palette

1. Actions palettemenu triangle

2. Default actions3. Delete selected

item4. Create new action5. Play selected

action6. Begin recording

action7. Stop playing or

recording action8. Expand list triangle9. Toggle dialog box

on/off10. Toggle item on/off


Table 2.8 Components of the Actions palette

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To begin recording an action, click the Create New Action button.The New Action dialog box appears (see Figure 2.17). Give the action aname and, if desired, assign it to a function key and color. Then, clickthe Record button and perform the functions you wish to include in theaction. When you are finished, click the Stop button. To save the set ofactions so that you may use them for future documents or on another

112 | C H A P T E R T W O | |

computer, press the Actions Palette Menu Triangle then choose SaveActions. You can also use the Actions Palette Menu Triangle to loadpreviously saved sets of actions. To use your completed action, you canpress the function key you chose or select the action and click the PlaySelected Action button.

Exercise 2.11 Recording an Action That Will Perform Tone Targeting

In this exercise, you will open a new copy of C2exercise.tiff thenrecord the operations necessary to perform tone targeting for the imagein an action.

1. From the File menu, choose Open.

2. Navigate to the Photoshop Student Files folder, then open theC2exercise.tiff (ÿ C2exer.tif) file. Click OK when the locked filemessage appears.

3. Click the Create New Action button on the Actions palette. TheNew Action dialog box appears (Figure 2.18).

Figure 2.18The New Actiondialog box

4. In the Name field, type “Target Offset Uncoated”.

5. Press the Function Key pop-up menu, then choose F2. (If F2 is alreadyassigned to another command on your system, choose anotherfunction key). Grayed-out F keys are already assigned. Click theShift checkbox. Finally, press the Color pop-up menu, then chooseRed.

6. Click Record. Notice the change in the Actions palette. The Recordbutton appears to be pressed and has turned red. The name of theaction to be recorded is selected and the Expand List Triangle pointsdown.

7. From the Image menu, choose Adjust, then select Auto Levels.



9. In the Shadow Output Levels field, type “25” and in the HighlightOutput Levels field, type “229” (the Output Levels fields in the Levelsdialog box should appear the same as Figure 2.10).

10. Click OK to close the Levels dialog box.


12. In the Gamma Input Levels field, type “1.75” (the Levels dialog boxshould appear the same as Figure 2.12).

13. Click OK to close the Levels dialog box.

14. Click the Stop button on the Actions palette.

15. From the File menu, choose Revert. When the alert appears, clickRevert.

The C2exercise.tiff (ÿ C2exer.tif) file returns to its previously savedcondition.

Exercise 2.12 Using a Recorded Action

In this exercise, you will use your Target Offset Uncoated action toperform tone targeting on two images.

1. If necessary, scroll so that your Target Offset Uncoated action appearson the Actions palette.

2. Click the Expand List Triangle so that the triangle points to theright (Figure 2.19).

This causes only the name of the action to be displayed in the list.

Figure 2.19The completedTarget OffsetUncoated actiondisplayed in theActions palette

1. Expand List Trianglepoints to the rightwhen only theAction name isdisplayed.

2. Play Selected Actionbutton.

1 2

114 | C H A P T E R T W O | |

3. Make sure the C2exercise.tiff image is active; its title bar will ( )have horizontal stripes in it or (ÿ) be highlighted if it is active.

4. Click the Target Offset Uncoated action on the Actions palette toselect it. Then, click the Play Selected Action button.

The prerecorded operations are automatically performed on thephotograph.

5. From the Image menu, choose Histogram. If you have correctlyrecorded the action, the data in the Histogram field will closelyresemble those in Figure 2.13.

6. Click OK to close the Histogram.

7. From the File menu, choose Open. Navigate to the Photoshop StudentFiles folder, then open C2exercise2.tiff (ÿ C2exer.tif). Click OKwhen the locked file alert appears.

8. Be sure the C2exercise2.tiff (ÿ C2exer.tif) image is active, then press plus F 2 . Note: You assigned plus F 2 to the Target Offset

Uncoated action when you completed the New Action dialog box. Ifyou assigned a different F key, use it instead of F 2 .

The series of actions recorded in the Target Offset Uncoated actionis performed on the photograph. It is now targeted for reproductionon uncoated paper using offset lithography.

9. Press the Actions palette menu triangle, then choose Save Actions.The Save Actions In dialog box appears.

10. Navigate to your Photoshop Files 1 disk or folder, in the Save ActionsIn (ÿ File Name) field, type “C1actions” (Figure 2.20), then click Save.

In the future you can load the same set of actions by pressing the Actionspalette menu triangle, then choosing Load Actions. Navigate to yourPhotoshop Files 1 disk or folder, then open your C1actions file.

Figure 2.20The Save Actions Indialog box


11. Close both C2exercise.tiff and C2exercise2.tiff (ÿ C2exer.tif andC2exer2.tif). Do not save any changes.

Printing Halftones with Photoshop

In practice, few professionals print halftones directly from Photoshop.Instead, they import saved Photoshop files into QuarkXPress, AdobePageMaker, or other desktop publishing programs and print completepages. However, you will often find it convenient to print proof or samplecopies of photographs from Photoshop to get an idea of what the finalreproduction will look like.

In Exercises 2.13 and 2.14, you will prepare your Project2.eps imagefor printing and output it on your laser printer or imagesetter. When youhave finished, you should compare your results with Figure 2.3. The targetingyou have applied during this chapter should result in a more pleasantreproduction than the uncorrected version that appears in Figure 2.3.

Preparing to Print PhotographsNOTE

To save the halftonescreen specifications inan EPS file, use thefollowing procedure:

• Open the Save dialogbox.

• Press the Format pop-up menu, then choosePhotoshop EPS.

• Click Save. The EPSFormat dialog boxappears.

• In the Preview pop-up menu, choose ( )PICT or (ÿ) TIFF 8bits/pixel. Mac usersshould use the TIFFpreview option if thefile is ever to be readby a PC.

• Click the IncludeHalftone Screenoption checkboxto save the halftonesceen informationwith the file.

• Click OK to savethe file.

Before printing a file using Photoshop, you must set several dialogboxes. You already know that you must set the Image Size and theHalftone Screen. However, Photoshop provides several other print-relatedoptions from which you can choose. These options are only useful whenyou print an image directly from Photoshop. In most cases, however,photographs are printed from within a page layout program. In suchcases, the print-related settings specified in the page layout programoverride those used in Photoshop. However, choices made with regardto Image Size always impact the quality of the photograph. And, as youknow, the halftone screen specifications set in Photoshop can overridethose used in a page layout program if the photograph is saved as an EPSfile and if the Include Halftone Screen option is activated.

When preparing to print, you must always check the Image Sizedialog box first. In particular, check the size and resolution of the image.Then you should choose File Info from the File menu (see Figure 2.22).In the File Info dialog box, you can include several bits of informationabout the image, including a caption, keywords that can be used to helppeople find the image if it is included in an image library, an appropriateAP (Associated Press) category, picture credits, information regardingthe origin of the photo, copyright information, and pertinent Internet

116 | C H A P T E R T W O | |

web page address. Many of these bits of information are most useful fornewspaper and periodical publishers. However, you may also find otheruses for them.

■ bleed After completing the File Info dialog box, Macintosh users shouldchoose a printer using the Chooser desk accessory. Both Macintosh andWindows users should then open the Page Setup dialog box (seeFigure 2.24). At this point, Windows users should choose a printer fromwithin the Page Setup dialog box. In addition to the options availablewhen using most programs, this dialog box contains nine options andfive buttons that open additional dialog boxes. You already know abouttwo of the buttons: you need to click the Screen button to set the halftonescreen specifications, and you should avoid using Transfer functions unlessyou are directed to do so by a service provider. Additional buttons allowyou to set a background color when printing to color slides, frame yourphotograph with a border, and create a bleed (when printing extendsbeyond the edge of the trimmed paper [Figure 2.21]).

Figure 2.21An example of aphotograph thatbleeds

1. Edge of printedsheet

2. Edge of sheet aftertrimming

3. Bleed margin4. Trim area

1

2

3

4


The nine options that can be chosen from the Page Setup dialog boxare summarized in Table 2.9 and illustrated in Figure 2.24.

Table 2.9 Page Setup options

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Exercise 2.13 Preparing an Image for Printing Using a Laser Printer

In this exercise, you will prepare Project2.eps for printing by makingentries in several dialog boxes.

1. From the Image menu, choose Image Size. The Image Size dialogbox appears.

Notice that the file is 58K in size, its dimensions are 4" × 2.847",and that it has a resolution of 72 ppi.

2. Deselect the Resample Image option (there should not be an “x” inits checkbox).


118 | C H A P T E R T W O | |

NOTE

You will notice thatin this exercise youwill repeat severalprocesses you learnedin Chapter 1. Youshould always followa sequence of steps toinsure that the imageyou output will be aquality photographand have the halftoneattributes specified forthe job. In particular, itis absolutely necessarythat you always checkand set the ImageSize dialog boxbefore printingany photograph.

4. Enter a Screen frequency of 50 lines per inch, then click the GoodQuality radio button. Click OK.

Examine the Print Size information at the bottom of the dialog box.Notice that the Resolution has changed to 75 ppi (remember thatyou chose a 50 lpi screen and that checking the Good Quality radiobutton multiplies the lpi by 1.5 to establish the ppi resolution) andthat Photoshop had to decrease the dimensions to 3.84" × 2.733"because there was insufficient data in the file to maintain the originalimage dimensions and provide a resolution of 75 ppi.

5. Click OK to close the Image Size dialog box.

6. From the File menu, choose File Info. The File Info dialog box appears(Figure 2.22).

Figure 2.22

1

2

3

The File Infodialog box

1. Choose a sectionfrom this pop-upmenu

2. Enter a caption ofup to 2,000characters in thisfield

3. Enter the name ofthe caption writer inthis field

7. Press the Section pop-up menu at the top of the dialog box. Noticethat it allows you to enter six different categories of informationabout the photograph. Choose each section from the pop-up menuone at a time and look at the dialog box that appears when eachsection is chosen. When you are finished looking at all six dialogboxes, choose Caption from the Section pop-up menu.

8. In the Caption section type “Natalie Jones wins makeup contest atYWCA competition!” In the Caption Writer section, type your name.Then click OK. The File Info dialog box closes.


9. From the Apple menu, choose Chooser. Use the Chooser to select alaser printer that has 300 to 900 dpi resolution. Check with yourinstructor, trainer, supervisor, or lab assistant if you need help withthis step. Close the Chooser.

ÿ Skip to Step 10.

10. From the File menu, choose Page Setup. The Page Setup dialog boxappears. (Macintosh users: If your computer is running AppleLaserwriter 8.4, you must press the pop-up menu labeled “PageAttributes” and choose Adobe Photoshop 4.0 to see the Photoshop-specific Page Setup choices.)

ÿ From the File menu, choose Page Setup. The Page Setup dialog boxappears. If necessary, click the Printer Name drop-down arrow, thenselect a laser printer that has 300 to 900 dpi resolution.

NOTE

The lpi is set low fortwo reasons: 1) thefile has too littledata to reproduce thephotograph using ahigher resolution; and2) we assume you areusing a laser printer toprint the file. Fifty lpiis about the maximumthese printers canaccommodate (see Table1.4 on page 43). If youhave a 300 dpi printer,you may wish to specify38 lpi.

11. Click the Screen button. Deselect the “Use Printer’s Default Screen”checkbox, then set the screen to 50 lpi, 45°, ellipse shape. Click OK.

12. Click the Border button. The Border dialog box appears. Type “2”in the Width field. Select points if necessary (Figure 2.23). Click OK.

Figure 2.23The Borderdialog box

13. Select all of the following options: (Note: The following list assumesyou have a PostScript printer. If not, some of the options may notexist or may have no affect.)

• Caption

• Calibration Bars

• Registration Marks

• Corner Crop Marks

• Center Crop Marks

• Labels

Your dialog box should look like Figure 2.24.

120 | C H A P T E R T W O | |

Figure 2.24The completed PageSetup dialog box

14. Click OK to close the Page Setup dialog box.

15. Save your changes.

Printing Halftones

After working your way through the necessary steps to prepare aphotograph for reproduction, the actual printing process will be relativelyeasy. You are given several choices in the Print dialog box, however (seeFigure 2.25 and 2.26). The options are listed and described in Table 2.10.

Table 2.10 Print dialog box options

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Exercise 2.14 Printing a Halftone Using a Laser Printer

In this exercise, you will print Project2.eps, then inspect the finishedreproduction.

1. From the File menu, choose Print. The Print dialog box appears(Figure 2.25). If you are using Laserwriter 8.4, you must press thepop-up menu labeled “General” and choose Adobe Photoshop 4.0to make some settings.

Figure 2.25The Print dialogbox—Macintosh

ÿ From the File menu, choose Print. The Print dialog box appears(Figure 2.26).

Figure 2.26The Print dialogbox—Windows

2. Choose the following options:

• Copies: 1

• Destination: Printer

• Encoding: Binary (on the Adobe Photoshop 4.0 page of AppleLaserwriter 8.4)

• Paper Source: Check with your lab assistant, trainer,supervisor, or instructor.

3. Click Print (ÿ OK). The photograph will now print.

4. Compare your printed copy with the one appearing in Figure 2.27.

122 | C H A P T E R T W O | |

Notice the following items:

• two types of Registration Marks

• Label (name of file) at the top

• 2-point Border

• Corner Crop Marks

• Center Crop Marks

• Calibration bar

• Caption

Figure 2.27Printed copy ofProject2.eps

1. Two types ofregistration marks

2. Label3. 2-point border4. Corner crop marks5. Center crop marks6. Calibration bar7. Caption

7

3

6

5

4

1 2

5. Look at the child’s face on your printed copy. Compare your printwith the image in Figure 2.3.

Notice the following about your copy:

• The shadows are lighter than those in Figure 2.3

• The midtones are lighter and provide more detail than themidtones in Figure 2.3

• Your reproduction looks better overall than Figure 2.3

6. Compare your printed copy to the image on the screen.

Notice how the printed version appears much darker than the imageon your screen. The dot gain inherent in laser printers, as well asmost printing processes, causes the midtones to appear darker onthe print than on the screen.


7. Save your changes.

8. If you have access to an imagesetter, and if you have permissionfrom your instructor, trainer, supervisor, or lab assistant, continuewith Exercise 2.15. Otherwise, continue with Step 9.

9. Quit Photoshop.

10. If you are saving your files on a disk, remove the disk from thecomputer.

Exercise 2.15 Printing a Halftone Using an Imagesetter

In this exercise, you will print Project2.eps on an imagesetter, makea proof, and inspect the finished proof. Complete this exercise only ifyou have an imagesetter and have permission from your instructor, trainer,lab assistant, or supervisor.

1. Use the Chooser to connect your computer to the imagesetter.

ÿ Skip to Step 2.

2. From the File menu, choose Page Setup. Make any changes that arenecessary to accommodate the chosen imagesetter. See your instructor,trainer, lab assistant, or supervisor for details. Do not change anyspecifications you made in the Halftone Screen dialog box duringExercise 2.12—the image does not have enough resolution to supporta higher lpi screen.

ÿ From the File menu, choose Page Setup. Click the Printer Namedrop-down arrow, then select an imagesetter. Make any changes thatare necessary to accommodate the chosen imagesetter. See yourinstructor, trainer, lab assistant, or supervisor for details. Do notchange any specifications you made in the Halftone Screen dialogbox during Exercise 2.12—the image does not have enough resolutionto support a higher lpi screen.

3. Be sure the following options are checked: Caption, Calibration Bars,Registration Marks, Corner Crop Marks, Center Crop Marks, andLabels.

4. Close the Page Setup dialog box.

5. From the File menu, choose Print. The Print dialog box appears.

6. Choose the following options:

124 | C H A P T E R T W O | |

• Copies: 1

• Destination: Printer

• Encoding: Binary (unless your imagesetter ornetwork requires ASCII)

• Paper Source: Check with your lab assistant, trainer,supervisor, or instructor.

7. Click Print (ÿ OK). The photograph will now print.

8. After the imagesetter has finished printing the page, process the filmaccording to the processor’s instructions.

9. Place the processed film on a light table. Turn on the table’s lights.

10. Examine the halftone dot structure with a 10 to 20 power magnifier.You should see 10% dots in the highlight areas and 90% dots in theshadows. Use a dot area meter if one is available.

If the imagesetter produced a negative, the opposite-sized dots(compared to the screen image) will appear on the film. For example,an area measuring 10% on the screen will be composed of 90%dots on the film, while an area measuring 90% on the screen will becomposed of 10% dots on the film.

If the imagesetter produced a positive, you will see the same sizedots as indicated in the screen image. An area measuring 10% in theK field of the Info palette will be composed of 10% halftone dots.

11. Make a proof of the negative. Use the type of proofing materialrecommended by your instructor, trainer, lab assistant, or supervisor.Follow the exposure and processing procedures for that material.(For purposes of this exercise, a photographic print, sometimes calleda Velox, is preferable.)

12. Examine the proof. Look for 10% dots in the highlights and 90%dots in the shadows. Examine the appearance of the midtones.

If you used photographic paper or other high-resolution proofingmaterial, you should notice that the image appears too light in themidtones. The midtones appear too light because dot gain has notyet been applied—dot gain occurs on the press, not on the film. Thelaser print appeared darker than this proof because images producedon laser printers contain dot gain. You need to become accustomedto viewing proofs that appear lighter than subsequent printed sheets.


Some proofing materials, especially those known as bluelines, donot produce high-resolution images. It may be hard to see thehighlight and shadow dots. In addition, the midtones might appearsomewhat unclear.

13. Compare your proof to the image on the screen and to Figure 2.3.

14. Quit Photoshop.

15. If you are saving your files on a disk, remove the disk from thecomputer.

Chapter Summary

In this chapter, you learned why tone correction is necessary and theprocedures used to perform basic tone targeting and correction. Tonesare identified using densitometric tone values, halftone dot values, andPhotoshop tone values. These values can be converted from one type toanother by using mathematical formulas. You can use Photoshop’s toolsto measure tone values in black-and-white photographs. Once a tone ismeasured, you can then classify it as a highlight, midtone, or shadow.The chapter also covered tonal range—what it is, how it is measured,what it means, and how it is displayed using the Histogram window.

Most importantly, this chapter covered some of the inherent attributesof various printing processes and the impact those attributes have ontone reproduction. In addition, the goal of halftone reproduction andhow to match a photograph to the specific needs of a particular printingprocess and substrate combination were covered. You learned theimportance of press fingerprinting, about the impact of dot gain, andhow to compensate for those factors using some of Photoshop’s tools.Photoshop’s tools that should be avoided when preparing images forprint production were also mentioned.

Once the tones in a photograph have been manipulated, you can setPhotoshop to print halftones using several dialog boxes, including thePage Setup, Print, Image Size, and File Info dialog boxes. Fewprofessionals print halftones directly from Photoshop. Instead, theyimport saved Photoshop files into a desktop publishing program andprint complete pages. However, it is often convenient to print photographsfrom Photoshop to be used as proofs.

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True/False Questions

____ 1. The density of a given area is measured with a dot meter.

____ 2. Photoshop uses values from 0 to 255 to describe tones.

____ 3. What you see on the monitor is what you get.

____ 4. You should not print to a file unless specifically instructed todo so by a service provider.

____ 5. Desktop scanners cause degradation of an image, especiallyin the shadow areas.

Multiple-Choice Questions

6. The goal of halftone reproduction is to

A. print a zero percent dot in the highlight density

B. print a solid layer of ink in the shadow density

C. print a 10% halftone dot in the highlight density

D. print the smallest consistently printable dot in the highlightdensity and the largest consistently printable dot in theshadow density

7. Which of the following tonal areas is most affected by dotgain?

A. highlights

B. midtones

C. shadows

D. specular highlights

8. Clicking the Auto button in the Levels dialog box causes whichof the following?

A. a 5% dot to appear in the highlight density and a 95%dot to appear in the shadow density

B. the gamma is automatically adjusted to match the printingprocess parameters

C. the halftone screen is automatically set to match therequirements of the imagesetter or printer

D. none of the above

Self-EvaluationReviewQuestions


9. Which of the following areas is generally reproduced withhalftone dots ranging from 30% to 70%?

A. highlights

B. midtones

C. shadows

D. solids

10. When preparing to print a file, the very first dialog box youmust always check is the

A. File Info dialog box

B. Page Setup dialog box

C. Image Size dialog box

D. Print dialog box

Fill-in-the-Blank Questions

11. __________ files can be processed much faster than thoseencoded in ASCII.

12. The __________ the gamma ratio, the flatter the curve andthe flatter the reproduction.

13. The phenomenon of halftone dots printing larger than theyare supposed to is called __________.

14. When working in the Levels dialog box, you can decrease thecontrast in an image by using the __________ sliders.

15. Which slick and dangerous command is designed for thosewho say, “I’ll know what it looks like when I see it?”__________

1. Measuring the Densitometric Values of a Photograph

1. Open ShortProjectC2.tiff (ÿ SPC2.tif), found in the PhotoshopStudent Files folder.

2. Use the Zoom tool to increase the magnification to 200% or300%.

3. Use the eyedropper tool to measure the halftone dot values. Youwill need to move around the image using the scroll bars.

ShortProjects

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4. Record the halftone dot values and complete the following table:

tseretnifoaerA eulavtodenotflaH tnelaviuqecirtemotisneD

ytisnedwodahS

ytisnedthgilhgiH

egnarlatoT

2. Interpreting the Histogram of a Photograph

1. From the Image menu, choose Histogram.

2. Complete the following table:

metIpohsotohPeulavenot

enotflaHeulavtod

cirtemotisneDtnelaviuqe

naeM

naideM

3. Which of these terms would best describe the tonal range of thisphotograph?

A. very dark

B. a little dark

C. a little light

D. very light

4. Close the Histogram window.

5. Save the photograph on your Photoshop Files 1 disk or folderas an EPS file with the name ShortProject2.eps (ÿ ShrtPro2.eps).Accept the default EPS settings in the EPS Format dialog box.

3. Adjusting Highlight and Shadow Dot Sizes

Assume that you have been instructed to prepare this image forreproduction using the gravure process on coated paper.




3. Check Table 2.3 to determine the appropriate highlight andshadow dot sizes for this reproduction.

4. Use the Output sliders or Table 2.6 and the Output Levels fieldsto specify the proper highlight and shadow halftone dot values.


4. Setting the Midtone Gamma

Assume that you have been told that a gravure press printing oncoated paper produces dot gain of 20%.


2. Adjust the gamma slider until the midtone dot sizes accommodatethe dot gain inherent in this printing process.


4. Save your work and close ShortProject2.eps (ÿ ShrtPro2.eps).

1. Preparing a Black-And-White Photograph for Print Reproduction

Assume that a client provides you with the file InDepthProjectC2.tiff(ÿ Idprojc2.tif) found in the Photoshop Student Files folder. You are toplan, set, and correct the photograph to meet the following specifications:

• The imagesetter outputs at 2,400 dpi.

• The printing process to be used is offset lithography.

• Glossy coated paper will be used.

• The specified printing process produces dot gain of about 15%.

• A 150 lpi, 45-degree, elliptical screen is specified.

• 256 shades are needed.

• The image needs to be 4" wide.

• The customer desires best quality resolution.

• The photograph should carry a caption stating “Fixer-uppertownhome available for only $185,000! Call 555-1432.”

• Include a caption, calibration bars, corner crop marks, and labelson all output.

In-DepthProject

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Using the given information, make all the necessary decisions andsettings needed to accurately reproduce this photograph using thespecified process/substrate combination. Be sure to make settings in allof the following dialog boxes (use this order):

• Image Size

• File Info

• Chooser Desk Accessory

• Page Setup

• Halftone Screen

• Levels—set highlight and shadows

• Levels—set midtone gamma

• Print

Save the file as InDepthProject2.eps (ÿ Indepth2.eps) on a new diskor folder named In Depth 2. In the EPS Format dialog box, be sure tocheck Include Halftone Screen. (Note: You can only print this file if youhave access to an imagesetter. Laser printers cannot handle thecombination of resolution and lpi that you have specified for this image.)

C Black-and-White Tone Targeting

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