Abstract

Discrimination thresholds in various directions from a standard color stimulus s₀ are represented by an ellipsoid in the (x, y, Y) space or, when the luminance Y is kept constant, by an ellipse on the chromaticity diagram. It has been a tradition since MacAdam (1942) to define thresholds by fluctuation of repeated color matchings under the assumption that the distribution of colors indiscriminable from s₀ is 3-D or 2-D normal f_N(s). This procedure cannot be applied to painted color samples and the discrimination ellipsoid around s₀ is defined through paired comparisons of s₀ and s_j, where s_j's are a set of prepared samples, j = 1, 2,…, n. As to method of obtaining an ellipsoid from these data, the situation is chaotic. Indow and Morrison (1991) proposed a procedure that is an extension of the method of constant stimuli for uni-dimensional stimulus continuum. Denote by P_j the rate that s_j is judged different from s₀ where s_j differs from s₀ in various directions Λ = 1, 2,…, n.

© 1992 Optical Society of America