Protanopic observers show nearly normal color constancy with natural reflectance spectra

Abstract

The ability of color-deficient observers to discriminate between illuminant changes and surface-reflectance changes in a scene was tested with natural and Munsell reflectance spectra. To avoid the confounding effects of spatial structure, stimuli were simulations of Mondrian-like colored patterns, presented on a computer-controlled color monitor. Protanopes performed less well than normal trichromats, regardless of the type of reflectance spectra, but they were least disadvantaged with patterns comprising reflectance spectra drawn from urban and rural scenes, more characteristic of the natural environment.

Figure 1

Detectability of changes in surface color during daylight illuminant changes of correlated color temperature 25000 to 6700 K for observers with normal trichromatic and protanopic color vision. Each contour represents a constant frequency of “illuminant-change” responses in the CIE 1976 (u′, v′) chromaticity diagram. Data are shown for Mondrian-like patterns of Munsell and natural reflectance spectra. The open squares and circles indicate, respectively, the chromaticity coordinates of the first and the second global illuminants on the pattern. The daylight locus and the protanopic confusion lines (P) are also shown.

Figure 2

Detectability of changes in surface color during daylight illuminant changes of correlated color temperature 4000 to 6700 K for observers with normal trichromatic and protanopic color vision. Other details as for Fig. 1.