in photography, technique for preparing coloured (colour printing) photographic prints in which the colours of the subject are resolved by optical filters (filter) into three components, each of which is recorded on a separate gelatin negative. The three negatives are converted into relief positives in which the depth of the gelatin is related to the intensity of the colour component; each image is then saturated with a dye of complementary colour, and the finished print is assembled by transferring the dyes one at a time, and in register, to a suitable surface.

Up to 150 prints can be obtained from a set of gelatin-relief positives simply by redyeing them and repeating the transfer. In the late 20th century, the development of a panchromatic matrix film made it possible to produce the relief positives directly from a colour negative.