Abstract

In 1886, Arthur König suggested that some perspective view of the chromaticity diagram might represent equally noticably different pairs of colors by equally spaced points. Judd published the first diagram on which that was attempted. A diagram based on Judd’s was recommended in 1960 by the International Commission on Illumination (CIE). The ratio of maximum-to-minimum radii of ellipses of equal noticeability was reduced on it from ~30:1 to ~7:1. In its 1976 recommendation, the CIE increased the vertical dimension by 50%. The ratio of maximum-to-minimum radii is still ~7:1. To do much better, it would be necessary to use a diagram that is not flat. Such a diagram is unusable. We can only hope to find a formula that will express every color difference in terms of differences of locations of points in the chromaticity diagram. Chickering published a formula (FMC1) that closely approximates the ellipses. The greatest ratio of corresponding radii is ~1.4:1. A formula to replace all previous formulas should be similarly derived from color-difference ellipsoids that represent observations by at least three observers who have normal color vision. Those ellipsoids should be obtained around at least twenty-five well-distributed chromaticities. At least ten should be obtained at three or more luminancefactor levels.

© 1985 Optical Society of America