ICC Colour Management for Print Production

ICCICC colorcolor managementmanagement forfor printprint productionproduction

TAGA Annual Technical Conference 2002 W Craig Revie Principal Consultant Fuji Film Electronic Imaging Limited ICC Chair of the Graphic Arts Special Interest Group

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow

• ICC History • ICC Objectives • ICC Membership • Working groups • Details from www.color.org

• 1990 PostScript Level 2 released by Adobe • 1993 FOGRA conference - Intercolor consortium formed • 1994 Apple’s ColorSync format adopted • 1994 Version 2 ICC profile format defined • 1995 Windows 95 with ICM • 1999 PDF 1.3 has support for ICCBased colorspaces • 2000 Photoshop 6 released • 2001 Version 4 ICC profile format defined • 2002 PDF/X-1a (and possibly PDF/X-3) standardized

• Open systems color management – Portable, standard color profile format – Framework independent of device capabilities • ‘Technical’ basis and broad membership – Develop a common understanding of color • Not limited to print production – Basis of profile connection space is a reflection print which may limit areas of application

• Founding members • Regular members • Honorary members •Observers • Steering committee – Founding members + elected members • Chair, vice chair, secretary and technical secretary – Lars Borg [Adobe], Uwe-Jens Krabbenhoeft [Heidelberg], Kip Smythe [NPES], Tony Johnson [London College of Printing]

• Focus on specific areas • Examples: – Architecture Working Group – Workflow Working Group – Graphic Arts Special Interest Group • Email discussion groups + 4 meetings per year

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow

• Basic colorimetry, CIE standard observer • RGB additive and CMY(K) subtractive color models • ‘Device independent’ color • Color transforms

Rod cells Cone cells

Response of cone cells to different The CIE standard observer frequencies of light

CIELab and CIEXYZ standards • based on CIE standard observer • describe colors as we see them • used in both PostScript and PDF

AdditiveAdditive colorcolor SubtractiveSubtractive colorcolor

Start with black and add Start with white and subtract red, green and blue red, green and blue

Many (but not all) colors can be simulated in this way © FujiFilm 2002 EachEach devicedevice ‘sees’‘sees’ colorcolor differentlydifferently

Photographic printer Image display Ink jet printer How can we convert colors from one device to another?

Digital camera Printing Scanner press

Photographic printer Image display Ink jet printer Colour transform jungle

Digital camera Printing M x N transforms press Scanner required

Color transform for Photographic Photographic device to standard printer printer color space and Image from standard color display space to device Ink jet TAG printer

TAG Standard TAG colour

TAG space TAG

TAG Digital camera Printing M + N transforms press Scanner required

Given a colour calculate ink percentage required to reproduce that colour

ICC Profile

BtoA tables

AtoB tables

Calculate colour produced by Standard color space given ink percentages Ink percentage [CIEXYZ or CIELab] [CMYK]

curve 1-D LUT values stored in profile ‘count’ samples

parameters defining one parametric curve of a standard set of functions in profile

e1 e2 e3 matrix coefficients e4 e5 e6 matrix stored in profile e7 e8 e9

e1 e2 e3 e10 matrix coefficients e4 e5 e6 e11 matrix with offset stored in profile e7 e8 e9 e12

multi-dimensional values at each node of the 3- or 4-D table LUT stored in profile

C L e1 e2 e3 R M e4 e5 e6 a e7 e8 e9 G Y b B K CMYK 1-D tables 4-D LUT Lab 1-D tables matrix parametric curves AToB tag from printer profile tags from monitor profile

C L e1 e2 e3 e10 e4 e5 e6 e11 M a e7 e8 e9 e12 Y b Lab 1-D tables Matrix with offset 'M' 1-D tables 3-D LUT CMYK 1-D tables K BToA tag from version 4 printer profile

Header

Private Public ICC Profile Inspector.lnk

A2B0 B2A0 A2B1 B2a1 A2B2 B2A2 A2B3 B2A3

• Rendering Intent • Profile connection space (PCS) • Color Management Module (CMM)

Solid shape indicates gamut of print process Wire frame indicates gamut of monitor When printing colors viewed on screen some kind of trade-off must be made to determine how we should map one color gamut to the other

Company logo

Tinted Areas

Illustrations

Photographs

Text

• Four ICC Rendering Intents define gamut mapping – Absolute Colorimetric: measurement (relative to illuminant) of output color should match that of input color if possible – Relative Colorimetric: measurement (relative to paper) of output color should match that of input – Perceptual: color images should be transformed to produce desired appearance on the output – Saturation: color transforms should maintain saturation in colors where possible

Color images should be transformed to produce desired appearance on the output - but how? Input ? profile 1 Output PCS profile Input profile 1 We need to agree a means to Images and input determine 'desired appearance' profiles are created with respect to the PCS independently of the output profile

Ah yes, not a D50, 500 lux light bad looking source virtual print

Media White Point has neutral reflectance of 89% (Dmin 0.0506) Media Black point has neutral reflectance of 0,30911% (Dmax 2.51)

CIE 1931 standard colorimetric observer adapted to viewing environment 20% surround

Color images should be transformed to produce desired appearance on the output

Input profile 1 Output PCS profile Input profile 1

Output profile creators can assume On input images and/or profiles that images have been adjusted to can be adjusted to achieve achieve desired appearance and desired result on (virtual) can perform necessary gamut reference medium mapping for printer

© FujiFilm 2002 OpenOpen question:question: HowHow bigbig // whatwhat shapeshape isis thethe PCSPCS gamut?gamut? • This is at present undefined • Given the density range that has been defined gives us an idea of size • ICC is studying the advantages and disadvantages of defining the PCS gamut more precisely • Perceptual gamut mapping is vendor specific - "beauty is in the eye of the profile creator"

Rendering Intent

Profile from Header Header Private Private Profile from document Public Public A2B0 B2A0 A2B0 B2A0 printer A2B1 B2a1 A2B1 B2a1 A2B2 B2A2 A2B2 B2A2 A2B3 B2A3 A2B3 B2A3

Input Output transform transform Combined transform

CMM - often part of OS usually

more than one option © FujiFilm 2002 ColorColor ManagementManagement ModuleModule (CMM)(CMM)

• Applies transforms implied by profile data • No formal ICC definition • Why multiple CMMs? – Handling TRC profiles – Chromatic adaptation – Interpolation algorithms – Private tags – Some minor differences of interpretation

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow

• Creating a scanner profile • Creating a monitor profile • Creating a printer or proofer profile • Creating a profile for a printing press • Profile testing

Input Display Output

May be Matrix+TRC Usually Matrix+TRC type Must be LUT- based type but is more but may be LUT-based Must contain PCS- usually LUT-based Must contain both Device- Device and Device- Must contain at least PCS and PCS-Device PCS intents for all Device-PCS table for tables for Perceptual Rendering Intents Perceptual Intent Intent

Color target patch colors ICC Profile valid for measured selected media Color target for when scanned media to be L*a*b* using reference profiled scanner settings

Header

Private Public

A2B0 B2A0 A2B1 B2a1 A2B2 B2A2 A2B3 B2A3 RGB Profiling package constructs profile

Reference scanner Note the media, scanner model and settings selected scanner settings - the profile isn't worth as much without them

Measure target patch colors Obtain standard digital camera color ICC Profile valid for target L*a*b* profiled viewing environment

Header

Private Public

A2B0 B2A0 A2B1 B2a1 A2B2 B2A2 A2B3 B2A3 RGB

Warning: for a digital camera the viewing environment may be Photograph target in intended significantly different from that profiled viewing environment In many cases the use of a standard Select reference camera colorspace may be a better option settings © FujiFilm 2002 CreatingCreating aa monitormonitor profileprofile

Measurement of each patch made and passed to profiling package ICC Profile valid for profiled monitor settings L*a*b*

Header

Private Public

e1 e2 e3 e4 e5 e6 e7 e8 e9

RGB Note the monitor model, settings (WhitePoint, gamma, brightness, Profiling package contrast...) and viewing images colored patches environment - the profile isn't from target in sequence worth as much without them on monitor © FujiFilm 2002 PrinterPrinter profileprofile creationcreation

Measurement of each patch made and passed to profiling package L*a*b* ICC Profile valid for printer when printing in 'reference state' on Establish printer profiled media 'reference printing state' and print Header Private Public characterization A2B0 B2A0 target A2B1 B2a1 A2B2 B2A2 A2B3 B2A3

UCR, TAC, Black Printer CMYK control etc defined CMYK patch description Note the printer reference printing state, media and profile creation parameters (in particular how the black printer was controlled) - the profile isn't worth as much without them © FujiFilm 2002 ClassesClasses ofof profileprofile (2)(2)

ColorSpace DeviceLink Abstract Named color conversion

Constructed from a Perform Can be used to Used to number of device profiles PCS-PCS communicate describe transforms - named color colorspaces Used by CMMs to cache eg removing palettes (sRGB->PCS) color transforms color cast between Limited applications applications support

CMYK CMYK Input Output Input PCS Output Profile Lab or XYZ Profile (A) (B)

- ‘Black’ text mapped to 4-color + New devices require a single profile - 'Dirty yellows' can be a problem - Some profile interoperability problems

CMYK Device CMYK Input Link Output (A) Profile (C)

- New profile required for each input/output combination + Individual colors can be mapped when the - Can not be used for Device Independent Color profile is created - Limited applications support

• Three options: – Profile Individual press • the only way if no similar standard printing condition exists – Print to standard printing condition • relatively small effort to create a profile – Use profile for standard printing condition and adjust output to suit individual press • a useful route when it isn't possible to print to a standard

• Accuracy – measure a profile's accuracy using a reference set of color patches – example IT8.7/3 basic set for a printer profile – Average and Maximum dE can highlight profiles with problems • Quality – use the profile to process a number of standard test images and view the result – example SCID images • Color accuracy vs color quality – just because a profile produces accurate color does not mean that the result looks good • Fitness for purpose – make sure that the profile contains all of the information that will be needed by those wishing to use it

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow

• Image color management – scanners, digital cameras, Photoshop • Document color management – Quark XPress, Adobe InDesign, PostScript, PDF, PDF/X • Proofer color management – digital proofers, soft proofing

Header Private Public A2B0 B2A0

Header Profile and image combination Private Public

e1 e2 e3 e4 e5 e6 adjusted together to produce Header e7 e8 e9 Private Public 'desired appearance' with A2B0 B2A0 respect to either the PCS or a A2B1 B2a1 A2B2 B2A2 target printing condition A2B3 B2A3 Workflow decision: Print-ready CMYK (closed) Profiled and sharpened RGB (open)

TAG

TAG DocumentDocument elementselements

Image capture TAG CMYK RGB

TAG pCMYK pRGB

TAG Image editing pGray Gray

TAG Named Colour Page composition

CMYK ICC managed Badly managed CMYK RGB CMYK RGB CMYK RGB

pCMYK pRGB pCMYK pRGB pCMYK pRGB

pGray Gray pGray Gray pGray Gray

Named Color Named Color Named Color

Colored elements Colored elements Some elements tagged converted to CMYK tagged with appropriate RGB elements present as soon as possible ICC profiles or PostScript CSAs ‘Incorrect’ color profiles Named colors used converted to process or spot separations

PostScript or PDF to RIP color printer - 'desired Color managed appearance' document management Cprint required Mprint

PDF or Yprint PostScript K RIP print Convert to PDF or PDF or PostScript PostScript Cpress RIP Mpress

Ypress

Kpress PostScript or PDF printed on press - 'desired appearance'

• Different types of page element managed differently • Each image may need to be managed differently • Rendering intent selection • Output-specific adjustments/selections • PostScript and PDF document descriptions • Trapping, overprinting and transparency • Perceptual Rendering Intent loosely defined • Handling device-color elements (default profiles)

• Colorspace arrays (CSA) • Colorrendering dictionaries (CRD) • UseCIEColor mechanism • Relationship between ICC and PostScript color management

D H 1 1 A L1 DD(D) 1 D (A) D (L) D0 H0 A L L A E A0 0 1 I1 DE(E) L L L B E I0 A B C XL XM XN M1 X F0 B1 M M M D (M) C J DB(B) A B C M M YL YM YN 1 1 Table B0 0 DF(F) N N N Z Z Z D F J0 A B C L M N Y 0 G1 K1 N D (G) C1 1 Image G0 G K0 DC(C) DN(N) C N0 Z pixel 0 values XW YW ZW

XB YB ZB CIEBasedDEFG colorspace CIEBasedABC color space dictionary

XW YW ZW

XB YB ZB T1 L1 A1 C X EL EA TP(P) L0 A0 Inverse T M Y P P P 2 X Y Z LX LY LZ AL AM AN PX PY PZ M1 B1 Q Q Q T (Q) EM EB Render X Y Z Q MX MY MZ BL BM BN B Y QX QY QZ M0 0 Table T Z R R R 3 X Y Z R R R NX NY NZ CL CM CN X Y Z N C TR(R) E 1 E 1 K N C C N0 0 T4

Type 1 CIE-Based color rendering dictionary

PDF/ICC Workflow ICC Input ICC Profile ICC Output RGB or CMYK Profile Connection Profile CMYK Input [A2B0] [B2A0] [Illuminant] Space(PCS) [Illuminant] Output [mediaWhitePoint] “Paper Relative” [mediaWhitePoint] […] Colorimetry […]

ICM ICM

Colorspace Color Rendering RGB or CMYK CIE XYZ Array (CSA) Dictionary (CRD) CMYK Input “Illuminant [WhitePoint] Relative” [WhitePoint] Output [RelativeWhitePoint Colorimetry [RelativeWhitePoint] […] […] PostScript Workflow

ICC Press Profile ICC Proof Profile

BtoA tables BtoA tables

AtoB tables AtoB tables

Step 2: calculate what Step 3: calculate what colors will be produced for CMYK values are needed each CMYK when printed to produce those colors Step 1: all document color on Press on Press B conversion to CMYK performed as if the document will be printed on press Digital proofer simulates a printing press or a well-defined printing process

• Element-based or raster-based color management • Preserving black-only elements • Avoiding ‘dirty’ yellows • Proofing spot colors

Enhanced Smart CMM processing Input Output appearance appearance

Appearance Appearance model data model data

Header Header

Private Public Public Private

A2B0 B2A0 A2B0 B2A0 A2B1 B2a1 A2B1 B2a1 A2B2 B2A2 A2B2 B2A2 A2B3 B2A3 A2B3 B2A3

INPUT OUTPUT Rendering Rendering Intent Intent Standard processing Standard CMM

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow

• Start with Press definition • Decide type of workflow – CMYK-early, Profiled RGB, Standard working space (sRGB) • Establish rules for allowed color data types (PDF/X) • Design workflow to minimize color conversions • Test individual elements before putting them together • Remember: garbage in still produces garbage out • Adopting industry standards where possible can save a lot of work!

Create Proof Press Proofer profile profile

CMYK

CMYK Print

CMYK All page elements converted to CMYK of target press Target Alternate Re-purpose press press Profile for target press profile profile included in document Limited re-purposing may be possible

Create Proof ICC X Press Press Proofer profile profile profile profile

ICC1

ICC2 ICC X Press Print profile profile

ICC3 All page elements tagged with an appropriate ICC profile ICC X Press Re-purpose Profile for target press profile profile included in document

Default RGB or Default Default CMYK profile profile profile Proof used to color Default Press Press Proofer manage data profile profile profile profile

Page element uses DeviceRGB Default Press Print or DeviceCMYK profile profile colorspace

Default Press Re-purpose profile profile

• Defined by ISO (ISO 15930-1) • Designed for 'blind exchange' • Based on PDF 1.3, documents must have: – all fonts and images embedded – all colored elements encoded as CMYK, spot or DeviceN – MediaBox, TrimBox and ArtBox defined – indication of whether file is trapped or untrapped – intended printing condition defined • Widespread industry support – SWOP, DDAP, Time Inc, RR Donnelley

• Currently being defined by ISO (ISO 15930-3) • For 'blind exchange' within color managed workflows • Based on PDF 1.3, documents must have: – all fonts and images embedded – colored elements encoded as CMYK or ICCBased (or equivalent) – intended printing condition defined – MediaBox, TrimBox and ArtBox defined – indication of whether file is trapped or untrapped • Widespread industry support – ECI, FOGRA, Time Inc

• Maintained by the ICC secretariat • Identifies standard printing conditions • Short and long name for each printing condition • Details given of how to obtain colorimetric data for printing process • RGB data registry currently under construction • Referenced by PDF/X-1a and PDF/X-3 standards

• About the ICC • ICC color management concepts • Creating ICC profiles • Using ICC profiles • Defining an ICC-based workflow • Questions and discussion