#COLOR19Oiling Your Color

Management MachineJohn Seymour

John the Math Guy, LLC

John the Math Guy

Color management in a nutshell

§Accurate communication of color between print buyer and printer

§Accurate production of color by printer

ICC Profile – the main tool

Converts fromone description

of color…

… into another

ICC Profile – the Rosetta StoneHieroglyphic

Demotic

Ancient Greek

ICC Profile – the main tool

Generally,one description

is device dependent...

… and the other is device

independent.

Dependent? Independent?

§Device dependent§CMYK§RGB§CMYKOGV

§Ambiguous

§Device independent§ L*a*b*§ sRGB§XYZ

§Standardized

ICC Profile to communicate intent

So that a given CMYK value…

… is interpreted as a given

L*a*b* value.

CGATS TR002, Fogra 54, ISO 15339 CRPC 2 … User specifies a profile

Communication profiles

§Based on hypothetical press§Running hypothetical inks§On hypothetical stock§With a hypothetical pressman

Testing artwork with a prooferJMG Times

CMYKvalues

L*a*b*values

CRPC 4, communication profile

Prediction profile

CMYKvalues

JMG Times

InstaProof

Producing artwork on pressJMG Times

CMYKvalues

L*a*b*values

CRPC 4, communication profile

Prediction profile

CMYKvalues

Prediction profile

Prediction profile?

Prediction profile

The IT8 test target

Prediction profile

§Press is set to standard condition when profiled§Press is reset to that same standard condition for

production

How do you reach this standard condition?

Oilhere

Oilhere

Oilhere

OilhereOil

hereOilhere

Oilhere

Oilhere

Oilhere

Color management isn’t all that complicated

Color management isn’t all that complicated• You just have to know where to apply the oil• And how much to apply• And what type of oil for each point

• Ok… maybe it is a bit complicated!

My view of what color management means• Applies to all places that affect color• Not just profiling the press• Today we talk about all those other places

Oiling the SOLID CMYK gear

Solid CYMK

• Targets defined in ISO 12647-2 and ISO 12647-6• May be defined in a CxF file• Substrate correction may be allowed/required• ISO 12647-2 (web offset) – target is L*a*b*, not density• ISO 12647-6 (flexo) – target is a CIELAB hue angle

What!??!?!?!

Perifarbe concept• Adjust ink strength or

film thickness• Run to the density

closest to target L*a*b*

Perifarbe in practice

Oiling Single-ink CMYK halftones

Oiling Single-ink CMYK halftones

Actual press Target

Tone valuein file

Tone valuefor plate

Oiling Single-ink CMYK halftones

• Set up plate curves to adjust

• Use the TVI formula (“Murray-Davies”) to match TVI curves in ISO 12647

Oiling Single-ink CMYK halftones (G7 method)

Single ink halftones of CMYK (G7 method)• Motivation

• Grays are more important than single color halftones• Common appearance is possible

• Specific CMY combinations (e.g. C50, M40, Y40) are ordered to be a specific gray

• Plates curves adjusted to make neutral

G7 in a single imageY40 41 423938

38

39

41

40

42

M

C50Want this to be gray

Single ink halftones of CMYK (G7 method)• Motivation

• Grays are more important than single color halftones• Common appearance is possible

• Specific CMY combinations (e.g. C50, M40, Y40) are ordered to be gray

• Plates curves adjusted to make neutral• Not fully compatible with TVI method – do one or the other• The results are similar, usually• ISO characterization data sets are based on G7

So far…

• Solids are adjusted at press• or maybe in the ink room?

• Halftones adjusted via plate curve to match either TVI or G7 spec

• Solids and plate curves plus communication profile might be good enough

Overprints?

Overprints

• Overprints are tough

Where was that overprint knob???

???

Overprints

• Overprints are tough• Depend on the solids• Depend on tack and opacity• L*a*b* target values are in 12647-2• But there are no DE tolerances

(Preucil) trap number• Could be a useful check• Could be misleading • Not recommended by ISO

Overprints

• Overprints are tough• Depend on solids• Depend on tack and opacity• L*a*b* target values are in 12647-2• But there are no DE tolerances• Where to put the oil?

So far…

• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI

or G7 spec• Overprints adjusted at press or ink room or ink

company or no where?

The rest of the CMYK builds

The rest of the CMYK builds

• Getting proper CMYK solids and TVI or G7 might be close enough?

• Assumes that your press “behaves like the hypothetical press”

• Example where they don’t – stochastic vs conventional dots

• Example where they don’t – two and three color overprints

• If not good enough, full on color management with profiles is necessary

Spot colors

• Target is • A cloth swatch• PMS number• L*a*b* value• Spectrum

• CxF

Spot color formulation

• Performed in ink kitchen• Can be adjusted by hand• More better to do with formulation software

Spot color formulation

Spot color on press• Big question

• Can we get there from here?

• … or do we need to go back to the kitchen?

Halftones of Spot colors• Usually not specified!• Use TVI for plate curves?

• What filter?• What TVI curve?

• Warning – TVI fails for rich colors and tints

• Use SCTV (Spot Color Tone Value)

So far…

• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI

or G7 spec• Overprints adjusted at press or ink room or ink

company?• Ink formulation software for spot colors• SCTV for plate curves of spot color halftones

Expanded gamut

• Will allow richer colors (orange, green, and blue) in images

CMYK gamut CMYK+OGV gamut

Expanded gamut

• Will allow richer colors (orange, green, and blue) in images

• (Big sell point) ~90% of spot colors can be printed with CMYKOGV

• Less cleanup between runs – huge savings for short run plants

Expanded gamut – downsides

• Expect to invest• Requires press profiling• Special software• Learning curve

• No universal standard set of inks• Red or orange?• Blue or violet?• Maybe CMYKOG?

• No industry standard 7-color profiles

EG color management of solids

• You decide O vs R, and V vs B• You decide target L*a*b* of O, G, and V

This gamut ain’t big enough for the both of us!!

Are we in the wild west?

EG color management of solids

• You decide O vs R, and V vs B• You decide target L*a*b* of O, G, and V• Same perifarbe stuff applies

EG color management of halftones

• TVI or SCTV?• Best guess today

• use SCTV for OGV• use TVI for CMYK

• In the future?• Perhaps SCTV for CMYK as well

Review• Solids are adjusted at press• Halftones adjusted via plate curve to match either TVI or

G7 spec• Overprints adjusted at press or ink room or ink company?• Ink formulation software for spot colors• SCTV for plate curves of spot color halftones• Expanded gamut

• use perifarbe to reach your target• use SCTV to set plate curves

This presentationis largely based on a webinar

I presented forTechkon USA, Feb 2018.

I gratefully acknowledge being permitted to reuse this

material.

#COLOR19 John SeymourJohn the Math Guy, LLC

john@johnthemathguy.comhttp://johnthemathguy.blogspot.com/

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John the Math Guy