Color Management Concepts

Transcription

1 Color Management Concepts ARNAB MAITI Regional Manager Prepress Solutions & Packaging Segment Graphic Communications Group

2 What is Color Management What is Management What is Color

3 A Little Understanding for Color(1) blue red gray Color violet cyan yellow

4 A Little Understanding for Color(2)?!

5 What is Color Color is Perception Red

6 What is Color Color is perception Lively red Knallrot Fire red!!! Dark red Dunkelrot Bright red

7 What is Color Management Color Management is managing the feeling! Red Because our feeling defines the Color!

8 Perception of Color Human Color perception: 3 stages Retina : RGB Ganglion: opponent colors red - green and blue - yellow (CIELab) Cortex[brain]: LCH

9 Color is a 3 dimensional Space RGBEBU RGBNTSC Lab LCH XYZ YCC

10 Color Calculation RGB XYZ Lab LCH YCC LCH XYZ Lab RGB XYZ We can calculate Color from one 3 dimensional Color Space to another 3 dimensional Color Space EXACTLY

11 Reason for Color Management Scanner Monitor Proofer Press Every device sees color different They work in different color spaces

12 Every device has its own color gamut Scanner Monitor Offset

13 MAPPING OF COLOR SPACES RGB scanner color space ICC Profile color space (gamut ) mapping RGB scanner CMYK printer Color management history CMYK printer color space ICC Profile simplified 2D-representation false colors, posterization or color shifts, if transformation not done properly

14 Color Publishing System Color? Input RGB Front End Applications (Photoshop, Illustrator ) RGB CMYK Output Monitor

15 Color Publishing System Closed systems components from one vendor limited number of components proprietary interfaces skilled users CMM integrated and hidden Open systems: DTP components of different vendors unlimited number of components open interfaces users with limited knowhow CMM users responsibility Good results! Unsatisfactory results!

16 Conventional Color Reproduction Color? RGB1 RGB RGB2 CMYK CMYK1 CMYK2 Equipment Management

17 And the real world? Scanner Monitor Proofer Press

18 Components of Color Management 3 Components of Color Management systems CMM: Color Matching Method [color transformation] Profiling - SW Applications

19 Essential of Color Management! RGB1 RGB RGB2 CMYK CMYK1 CMYK2

20 Scanning Methods Scanning Mirror PMT Whereas a digital camera creates a picture, a scanner reproduces an already existing one. Two technologies are available for this: CCDs (charge coupled devices) for flatbed scanners, and PMTs (photo multiplier tubes) for drum scanners Mirror Color filter PMT Light source Mirror Cathode Dynode Anode CCD element Mirror CCD element Elements

21 Color Publishing System(Input)! Input RGB Transformation CIELab Input System should give the COMPLETE information of the Original

22 Color Publishing System(Output 1)!! CIELab Transformation RGB Monitor

23 Color Publishing System(Output 2)!! CIELab Transformation CMYK Output

24 Components of Color Management Color Management tools Needs of a Color Management system? Color Matching Method for color transformation Processing Device - profiles for characterization Applications

25 Components of Color Management Color Matching Method Tasks: makes color transformations Organisation: Target: integrated in OS Mac : in OS; ColorSync PC : Win 98, Win 2000: in OS Win NT, Win 95: part of applications

26 Color Management in System Color Management idea and principle: Scanner A RGB device device independent, independent, standardized, standardized, complete complete Monitor A RGB Scanner B RGB Scanner C RGB Scanner D RGB Photo CD RGB Digit. Camera RGB Video RGB ICC-Profile CieLab ICC-Profile Monitor B RGB Euroscale CMYK SWOP (USA) CMYK Japan CMYK Newspaper CMYK Color printer CMY (K) Profile connection space: CIELab

27 Color Publishing System with CM Input RGB Transformation CIELab Uniform System Color Space CIELab (ColorSync, ICC) Transformation CMYK Output Transformation RGB Monitor

28 Color Publishing System with CM Remember Color Management is only possible with a system based on CIELab (human feeling)! +b -a +a -b

29 Color Standard Commission Internationale d`eclairage (CIE) Specification of Lab color space 1976 Device independent Based on the human visual sense International Color Consortium (ICC) Specification of ICC profile format 1994 Platform independent Manufacturer independent

30 Tools and Methods of Color Management

31 Color Management Tools Input RGB Transformation Generation of scanner profiles Generation of monitor profiles Transformation RGB Monitor Generation of print profiles Transformation CMYK Output

32 Profile Generation of Input Device Profiling of input devices: Scanner- and digital camera- profiles Generated profile is only valid for a device + setting [Kodak-, Fuji-film]. Reference Colorimetric measurement Lab ICCprofile Scan RGB Comparison generate

33 How does it work... Scanner ICC Generates ICC-input profiles For scanners but also for other input devices eg. digital cameras

34 How does it work... Scanner ICC Uses test targets of all main film manufacturers Reflective, transmission IT 8-Originals 8 from Kodak, Fuji and Agfa (Match Targets incl. diskettes with average Color values) Calibration profiles for all purposes More then a Scanner calibration eg.. How does my scanner sees the colors of a Kodak transparency?

35 How does it work... Scanner ICC Generation of scanner profiles scanned IT8.7 original ICC ICC scanner-profile reference-color values Scanner ICC software Supported Testcharts Agfa, Fuji and Kodak materials transparent/opaque, special materials

36 Profile Generation of Display Device Profiling of display devices: Display- resp. monitor - profiles Generated profile is only valid for a + setting [brightness/contrast] Reference Colorimetric measurement Lab ICCprofile Comparison generate Colorimeter present test images RGB

37 How does it work... Monitor ICC Generation of monitor profiles Generation of monitor profiles for all Macintosh Color monitor Inclusive measuring device Gamma curves are not changed

38 How does it work... Monitor ICC Generation of monitor profiles Adjust brightness and contrast Measure Color targets with measuring device on monitor Generate profile Profile generation in a few minutes

39 How does it work... Monitor ICC Generation of monitor profiles Color measuring device ICC ICC-monitor-profile Monitor ICC software Supported measuring devices Sequel Chroma 3, X-Rite X DTP92, Gretag spectrolino, Colortron.

40 How does it work... Little theory for the printing (1): Print ICC Generation of print profiles UCR: Under Color Removal (What is Under Color?) GCR: Gray Component Replacement Dot Gain: The difference of definition and printing at 45% screening USM: Unsharp Masking

41 How does it work... Little theory for the printing (2): Color Space of print Process Print ICC Generation of print profiles From a 3 dimensional Color Space (Lab, RGB) to a 4 dimensional Color Space (CMYK) Feedback from the printing process: Gamut Mapping

42 Gamut Mapping Gamut mapping: Devices have different gamuts Best - to - fit of different gamuts by transformation of perceivable colors onto actual gamut offset print monitor slide

43 Gamut Mapping Gamut mapping like a sponge strong extern weak intern

44 Gamut Mapping Gamut mapping: Gamut mapping is usually very complex and highly non-linear Determines quality of profile and color transformation independent evaluation: Different CMM s make only slight differences in the reproduction. The choice of CMM makes far less difference than the choice of profiling SW. dependent on task context [normal transformation versus proofing] controlled by rendering intents Dependent on color location because of human perception

45 Profile Generation of Output Device Profiling of output devices: Output - resp. printer profiles Determine color gamut of process optimize gamut mapping / minimize differences generated profile is only valid for a device + setting [paper sort, inks] Reference Colorimetric measurement Lab ICCprofile Print Comparison generate CMYK

46 How does it work... Print ICC Generation of print profiles color measuring device ICC ICC-output-profile printed testchart Print ICC software Supported measuring devices Gretag SPM series, Gretag spectro scan, X-Rite Digital Swatchbook,, Colortron II...

47 How does it work... offers many setup possibilities: Gamut Mapping Dot gain UCR & GCR Gray balance etc... PrintOpen ICC Generation of print profiles For presses and special applications

48 How does it work... Profiles for individual print processes Special profiles... for newspaper print... for gravure printing... for flexoprint... for silk screen printing... for every specialized print process Print ICC Generation of print profiles

49 How does it work... ICC profile generation: Highest quality through outstanding Color know how and experience 32 x 32 x 32 = Reference points Works with many manual and automatic spectral photometers Print ICC Generation of print profiles

50 Color Management Tools... The real world with Color Management Scanner Monitor Proofer Press

51 Color Proofing Workflow with Color Management

52 What is proofing Press Result? Prepress System CMYK Press Proof is to see the result of the printing process in ADVANCE.

53 Conventional Proofing... Prepress System CMYK Proof CMYK Press

54 What Proofing Should Be Prepress System CMYK ICC Press Press Color Space CIELab Proofer CMYK

55 Digital Proofing Workflow! CIELab Press ICC Profile CMYK Press ICC Profile CIELab! CIELab Proofer ICC Profile CMYK

56 Digital Proofing Workflow Example for practical CMM use softproof Dis Lab p Lab Out t Out Lab Color consistency by CMM Applications In Lab API CMM Heidelberg-CMM OS Lab Out

57 Profile as Result ICC - Profiles: Characterisation of devices input devices output devices display devices describes the properties of the device in different contexts

58 Profile Classes: Class I Input profiles device dependent CIELab Display profiles CIELab CIELab device dependent device dependent Output profiles CIELab CIELab device dependent device dependent CIELab CIELab device dependent device dependent

59 Profile Classes: Class II Color space conversion profiles standard colorspace CIELab srgb CIELab Device link profiles device dependent device dependent Abstract profiles CIELab CIELab Named color profiles CIELab indexed colors

60 Gamut Mapping and Rendering Intents Control of gamut mapping by rendering intents perceptual 0 visually optimal relative 1 conservation of luminance saturation 2 conservation of chroma absolute 3 no mapping in L

61 Rendering Intents Rendering intents: Rendering intents powerful, but dangerous tool False selected rendering intents - bad results

62 Rendering Intents by Proofing Example for paperwhite simulation on / off on off EuroOffset 375 K85 Newspaper IFRA GCR70 Newspaper IFRA GCR70

63 Inverse Gamut Mapping Inverse gamut mapping: try to get the original gamut back

64 Interface between Prepress and Press CIP3: What is CIP3? CIP3 stands for "Cooperation for Integration of Prepress, Press and Postpress" PPF (Print Production Format): able to hold the following information: Job and administrative data (in the admin block) Low-resolution bitmaps of press sheets Transfer curves Register marks Color and density measurement patches Cutting and folding information

65 CIP3 Advantages Improved quality monitoring (fully automatic) Faster production cycles (due to shorter makeready times and reduced operator error) Lower costs (less waste paper, shorter makeready times, no plate scanner needed) Simpler plate handling (because they don t need to be scanned) Automation, streamlined production (the data is available in one file for all stages from prepress to finishing) Future-oriented: open for future developments

66 Introduction - Overview This is the workflow for Process calibration CMYK Print Lab Print ICC Measurement Lab* Press Profile

67 Method and Tools to control the Quality Step 1 Step 2 Step 3 ABC ABC Standardization Measurement, Calculation Calibration Workflow Process in Press

68 Kodak,