Thread View: adobe.colormanagement
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Started by Gernot_Hoffmann
Thu, 05 Mar 2009 12:56
CMYK encoding for printer targets
Author: Gernot_Hoffmann
Date: Thu, 05 Mar 2009 12:56
Date: Thu, 05 Mar 2009 12:56
35 lines
1608 bytes
1608 bytes
For instance the target ECI2002CMYKi1(A3)_1_2.tif contains - according to the reference file - CMYK numbers by steps of 10, some values by steps of 5 and some single values 3 and 7. The maximum is 100. All tests by CS2. Let's consider for a patch with one value 70.0 the indicated numbers: Photoshop 8bpc: 70% Photoshop 16bpc: 70% Photoshop 32bpc: 0.698 Illustrator: 0.698 0.70*255 = 178.5 Wrong rounding 178 178/255 = 0.698 Aha, it's a problem of mapping 0..100 to 0..255 and eventually of wrong rounding. This leads to the conclusion, that CMYK values in the TIFF should be defined as integer numbers 0..255 and that the reference file should contain decimal numbers with sufficient accuracy in this format: ###.## . It's perhaps not really essential for the accuracy of a calibration, but why should everything be based on a wrong concept ? By the way: I think I've solved the problem, how to modify targets for a guaranteed inklimit, if this should be still interesting. Best regards --Gernot Hoffmann
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