Abstract: A process of forming on a copying material from an original having respective minimum and maximum density values D.sub.min and D.sub.max a copy having respective minimum and maximum density values P and Q, different from D.sub.min and D.sub.max, comprising the steps of: forming first and second non-superimposed test wedge images by exposing first and second specimens of the copying material to light of respective first and second colors, the exposure of the first and second specimens being such that the respective average exposure times are T.sub.B and T.sub.G, with the exposure to light varying across each specimen according to a preselected relationship, determining from the first test wedge image the density values D.sub.1 and D.sub.3 which an original must have to produce upon the copying material the respective density values P and Q if the copying of such original onto the copying material is performed with light of the first color for an exposure time T.sub.