The invention is a process for producing an optimised printing form comprising printing onto a substrate with a printing form with predetermined raster percentages on the printing press to obtain a test print in form of a stepped wedge with raster patches, measuring the reflectance spectrum of each raster patch, determining associated colorimetric values L*,a*,b* from the reflectance spectrum, transforming the colorimetric values L*,a*,b* for each raster patch in linear correlation with the color perception of the human eye, using the formula.times..times..times..times..times..times..times..times..times..ti- mes..times..times..function. ##EQU00001## wherein RCD is the relative colorimetric difference expressed as a percentage and represents an actual raster percentage achieved on the printing press, determining dot gain for each raster patch, correcting the predetermined raster percentages of the printing form by the determined dot gain, and producing an optimised printing form using the corrected raster percentages.