Colour Reproduction Indices and Acceptability of Prints at Controlled Density Levels

Abstract

The correlation between a Colour Reproduction Index (CRI) and a single stimulus, forced-choice, scaling of the acceptability of colour prints is examined. The prints were obtained from normally-exposed negatives, each scene photographed included a calibrating Macbeth ColorChecker Chart for colorimetric purposes. Each negative was printed to give a standard ideal reproduction, according to objective criteria, and a systematic array of controlled colour perturbations, a ring-around. Further sets of prints were made by reprinting additional ring-arounds at two lighter and two darker controlled density levels. Prints were assessed by twenty observers, using a standard viewing booth, with the included Macbeth Chart hidden from the observer by an opaque grey mask. The reproduction of the Macbeth Chart in each print was also measured spectrophotometrically and CRI values were calculated. A linear relation exists between CRI and the level of acceptability of each print in a constant lightness set. Comparisons are made with previously published results in estimating weightingsfor subsidiary indices in the calculation of CRI values.