Method of adapting a printing process while maintaining black build-up
A method of adapting color values, which have been produced for a first printing process to a second printing process, is performed so that the visual impressions of the colors in the two printing processes are identical. Starting from a first printing process adaptation U without maintaining the black build-up, which transforms the color values [C1,M1,Y1,K1] of the first printing process into color values [C2,M2,Y2,K2] U of the second printing process, and a second printing process adaptation V while maintaining the black build-up, which transforms the color values [C1,M1,Y1,K1] of the first printing process into color values [C2,M2,Y2,K2] V of the second printing process, a new printing process adaptation W is determined by weighted averaging of the transformed color values [C2,M2,Y2,K2] U and [C2,M2,Y2,K2] V .
1. A method for producing a printing process adaptation with which color values of a first printing process are converted into color values of a second printing process so that black build-up of the first printing process being substantially transferred into the second printing process and visual impressions of printed colors in the first and second printing processes being substantially identical, which comprises the steps of:
performing a first printing process adaptation without maintaining the black build-up for transforming all the color values of the first printing process into transformed color values of the second printing process;
performing a second printing process adaptation while maintaining the black build-up for transforming all the color values of the first printing process into further transformed color values of the second printing process;
performing a third printing process adaptation for transforming all the color values of the first printing process into additional transformed color values of the second printing process by performing a weighted averaging of the transformed color values of the first printing process adaptation and of the further transformed color values of the second printing process adaptation;
carrying out the weighted averaging with a weighting function f(C1,M1,Y1) derived from a proportion of chromatic printing inks CMY in colors of the first printing process;
using a function s(C1,M1,Y1) for forming the weighting function f(C1,M1,Y1), which is limited to a value range between 0 and 1, the function s(C1,M1,Y1) being a measure of an entire proportion of the chromatic printing inks CMY in a color of the first printing process; and
defining the function s(C1,M1,Y1) by s(C1,M1,Y1)=C1×C1+M1×M1+Y1×Y1.
2. A method for producing a printing process adaptation with which color values of a first printing process are converted into color values of a second printing process so that black build-up of the first printing process being substantially transferred into the second printing process and visual impressions of printed colors in the first and second printing processes being substantially identical, which comprises the steps of:
performing a first printing process adaptation without maintaining the black build-up for transforming all the color values of the first printing process into transformed color values of the second printing process;
performing a second printing process adaptation while maintaining the black build-up for transforming all the color values of the first printing process into further transformed color values of the second printing process;
performing a third printing process adaptation for transforming all the color values of the first printing process into additional transformed color values of the second printing process by performing a weighted averaging of the transformed color values of the first printing process adaptation and of the further transformed color values of the second printing process adaptation;
carrying out the weighted averaging with a weighting function f(C1,M1,Y1) derived from a proportion of chromatic printing inks CMY in colors of the first printing process;
using a function s(C1,M1,Y1) for forming the weighting function f(C1,M1,Y1), which is limited to a value range between 0 and 1, the function s(C1,M1,Y1) being a measure of an entire proportion of the chromatic printing inks CMY in a color of the first printing process; and
defining the weighting function f(C1,M1,Y1) by f(C1,M1,Y1)=min{s(C1,M1,Y1)/(T×smax); 1}, where smax is the maximum value of the function s(C1,M1,Y1).
3. The method according to claim 2 , which further comprises:
using a limiting factor T for determining at which chromatic color proportion s(C1,M1,Y1) solely the first printing process adaptation is used as the third printing process adaptation.
4. The method according to claim 3 , which further comprises:
determining a value of T=0.2 as a limiting factor.