Categorical color rendering of four common light sources

Subjects were asked to sort samples from the Optical Society of America (OSA) Uniform Color Scales set into 33 color categories under four separate illuminants: tungsten-incandescent, metal halide, high-pressure sodium, and clear mercury. Sorting required that each color sample be designated as a “good,” “acceptable,” or “poor” example within one of the eleven basic color categories specified by Berlin and Kay. Three indices of the categorical color-rendering capacity of the sources were developed. Assuming tungsten-incandescent as the reference illuminant, all three measures rated the color-rendering quality of the tested illuminants from best to worst in the order listed above, in agreement with the CIE color-rendering index.