Using ΔE metrics for measuring color difference in hard-copy pictorial images

摘要

Current color difference metrics such as ΔE*_(ab), ΔE*_(94), and ΔE_(00) were developed using uniformly colored patches. The quantification of color variation in pictorial images is far more complex and generally requires the use of sophisticated color appearance models such as CIECAM97s and CIECAM02. In a recent study of printer color variation, the question was raised as to whether, in certain well-bounded situations, ΔE metrics could be used as a measure of color difference in pictorial, hard-copy images. A psychophysical scaling experiment was designed and conducted to examine this possibility. In the experiment, observers rated test prints of three scenes relative to anchor prints for apparent color difference. The correlation between observer's scaling values of color difference for pictorial images and ΔE*_(ab), ΔE*_(94), and ΔE_(2000) was examined. It was found that, for the color shifts that were introduced into the test prints under constant media and viewing conditions, the ΔE metrics were effective measures of color variation in pictorial image samples. It was also found, however, that the efficacy of these metrics depended strongly on how the metrics were calculated. The procedure of using colors representative of the important colors in the prints being measured produced significantly better results than other methods of calculating the ΔE metrics.