Patent ID: 7586656

Claim:
A process for producing a printing form for use on a printing press, comprising the following steps: A) providing a printing form with a defined print image having specified raster percentages and containing at least one stepped wedge comprising a raster patch at 0%, a raster patch at 100%, and at least one other raster patch at a predetermined percentage; B) printing onto a substrate with the printing form provided from step A) with a printing ink on the printing press to obtain a test print of the at least one stepped wedge, where the raster patch at 0% corresponds to the color shade of the substrate, and the raster patch at 100% corresponds to solid shade of the printing ink; C) measuring a reflectance spectrum using a spectrophotometer, and determining associated colorimetric values L*,a*,b* from the reflectance spectrum, for each of the raster patch at 0%, the raster patch at 100% and the at least one other raster patch of the at least one stepped wedge of the test print, D) transforming the colorimetric values L*,a*,b* for the at least one other raster patch in linear correlation with the colour perception of the human eye, using the formula RCD = ( L * ⁢ rasterpatch - L * ⁢ substrate ) 2 + ( a * ⁢ rasterpatch - a * ⁢ substrate ) 2 + ( b * ⁢ rasterpatch - b * ⁢ substrate ) 2 ( L * ⁢ solidshade - L * ⁢ substrate ) 2 + ( a * ⁢ solidshade - a * ⁢ substrate ) 2 + ( b * ⁢ solidshade - b * ⁢ substrate ) 2 · 100 ⁡ [ % ] wherein RCD is a relative colorimetric difference expressed as a percentage, and represents an actual raster percentage achieved on the printing press, E) determining a dot gain for the at least one other raster patch based upon a difference between the predetermined percentage of the at least one other raster patch of the plate and the RCD percentage obtained in step D); F) correcting the predetermined raster percentage from the printing form by the dot gain from step E), thereby creating a corrected raster percentage for the at least one other raster patch; and G) producing a printing form with a print image using the corrected raster percentage obtained for the at least one other raster patch in step F).