Abstract: Apparatus and associated methods employed therein, for objectively providing an accurate appearance match between images produced by two imaging systems (e.g. a target image produced by one such system, e.g. a press sheet (140) generated by a printing press (130), which is to be matched by a replica image produced by another such system, e.g. a proof (120) generated by a color halftone proofing system(110)) and thereby calibrate the performance of one imaging system, e.g. the proofing system, to that of the other system, e.g. the printing press. Specifically, measurement data, such as illustratively densitometric N,R,G,B measurements, is obtained for the same portions of the press sheet and proof. This data is then transformed into a color space which encodes color information in a pre-defined manner that approximates color preferences inherent in human color interpretation.