Printing images on coloured substrates is an interesting challenge, since observers are partially adapted to the colour of the substrate. Existing colour management methods are not appropriate for coloured papers, since they ignore this partial adaptation and also experience problems in compressing the coordinates of the original to the gamut that can be reproduced on the substrate.
In the first two experiments, it was found that the degree of adaptation to a background colour was not dependent on the lightness or chroma of the background, and could thus be modelled with a constant degree of adaptation.
In the second experiment, different methods of determining the coordinates to print on coloured substrates were compared. A method in which the coordinates for printing on white, adjusted by a partial adaptation model using a degree of adaptation of 0.66, gave better results than the other methods tested. The method works best on papers of low colour strength, since as the colour strength of the substrate increases, the available colour gamut is reduced and the performance of different methods becomes more similar.