New Color-Matching Ellipses

TLDR: Three new sets of color-matching experiments have been made by three observers binocularly viewing a bipartite field of a three-primary colorimeter, and it appears that fundamentally different line elements can reproduce almost equally well a given set of color -matching ellipses.

Abstract: Three new sets of color-matching experiments have been made by three observers binocularly viewing a bipartite field (each half subtending 3°) of a three-primary colorimeter. Each set of color-matching data refers to 28 test colors scattered over the chromaticity gamut provided by the colorimeter. The luminance of each test color was 12 cd · m−2; the white surround (subtending 40°) was maintained at 6 cd · m−2. The elliptical cross sections (for Y = const) of the observed color-matching ellipsoids are compared with results previously published by MacAdam, and Brown and MacAdam. In view of the inherent experimental uncertainties of data of this kind, the new color-matching ellipses correlate well with those obtained by Brown, and Brown and MacAdam, but show significant deviations from those obtained by MacAdam’s observer P. G. Nutting, Jr. The discrepancies are puzzling. A note of caution is added with regard to the usefulness of color-matching ellipses in testing line elements. A set of color-matching ellipses can reveal only little of the visual mechanism that governs the precision of color matching and its assumed direct correlation with judging small color differences. It appears that fundamentally different line elements can reproduce almost equally well a given set of color-matching ellipses.