Color constancy in shadows.

Abstract

Because color samples perceived as surfaces or objects tend to look much the same under various viewing conditions, they are said to possess color constancy. The viewing condition chosen for study was an obvious shadow of daylight quality falling on a color sample and part of a surrounding white field; the less the effect of the shadow on the color appearance of the sample, the greater would be the color constancy. The purpose of the study was to make evaluations of the color constancy, both over all and by attributes, of ten color samples viewed one at a time under the standard shadow. The method was to present the color samples in the surface mode of appearance and to match them with a calorimeter, the field of which was also perceived in the surface mode. In some trials the shadow was present, in some absent, and in others there was no perceived shadow but rather the sample luminance alone was reduced proportionally. These match data were converted to the Munsell system of renotation. Brunswik-type constancy ratios were formed in terms of Munsell hue, chroma, and value taken separately. The results indicate the constancy of the hue, saturation, and lightness of the surface color perceptions. There was evidence of considerable constancy in all three attributes. After weighting the data for each attribute in accordance with an appropriate color difference formula, an estimate of the combined or over-all color constancy was obtained.