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Problems with ICC color conversion

Potential problemsBlack point compensationCMYK –> CMYK conversionGrayscale –> CMYK conversionPure color conversion

SolutionsMany solutions from different vendorsAvoid critical color spaces

GWG preflight profilesClassic (CMYK)ICC

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Black Point Compensation (BPC)

BPC is not part of ICC architecture and todaypreference cannot be included in PDF file.

C CMY

K

Without BPC With BPC

meter in ISO 32000-2 (PDF 2.0)

MY

K

BPC will be a para

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ICC color transformation architecture

Conversion of color spaces by using a intermediate Profile Connection Space)

RGB

CMYK

LABPCS

color space (PCS =

RGB

CMYK

LAB

CMYK –> CMYK conversion

Different black separation

CMY

K

CMY

PCS

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K

Grayscale –> CMYK conversion

Grayscale (K only) is converted to 4C (CMYK)

CMY

K

CMY

PCS

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K

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Pure Black appears in all four process colorseparations (and get screened!)

Pollutio lors (and screening!)

,,,,0% C....0% M....0% Y

..45% C

..34% M

..33% Y

..87% K

0 / 100 / 10 1 / 98 / 85 / 5 1 / 98 / 85 / 5

PCS

Pure color conversion

T T

Illustration: Florian Süssl

n of pure co

100% K

0 / 0 PCS

© Stephan Jaeggi, PrePress-Consulting

Many solutions from different vendors

Diff available

Propriet nt predictable results!

erent options

ary solutions preve

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Solution: avoid critical color spaces

Device independent color (with ICC profiles)RGB imagesCMYK images which differ from output intent(Attention: risk of new black separation!)

Device dependent color (no ICC profile)CMYK images which already correspond to OI(that’s even required in PDF/X-4)CMYK vectorsCMYK text

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GWG V1…4 preflight profiles

Error

OK

OK

Text/Lineart

ErrorDeviceRGB

OKDeviceGray

OKDeviceCMYK

ImagesObject Type

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GWG V5 preflight profiles

ErrorErrorDeviceRGB

ErrorErrorICCbased RGB,CalRGB

ErrorErrorICCbased Gray,CalGray

ErrorErrorICCbased CMYK

OKOKDeviceGray

OKOKDeviceCMYK

Text/Lineart

ImagesObject Type

ClassicDelivery method

© Stephan Jaeggi, PrePress-Consulting

GWG V5 preflight profiles

ErrorErrorErrorErrorDeviceRGB

WarningOKErrorErrorICCbased RGB,CalRGB

ErrorErrorErrorErrorICCbased Gray,CalGray

ErrorWarningErrorErrorICCbased CMYK

OKOKOKOKDeviceGray

OKOKOKOKDeviceCMYK

Text/Lineart

ImagesText/

LineartImagesObject Type

ICCClassic (CMYK)Delivery method