potential problems with icc color conversions...© stephan jaeggi, prepress-consulting problems with...
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© Stephan Jaeggi, PrePress-Consulting
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
© Stephan Jaeggi, PrePress-Consulting
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
© Stephan Jaeggi, PrePress-Consulting
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
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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