Showing papers on "Color constancy published in 1981"

Chromatic Adaptation in the Honeybee: Successive Color Contrast and Color Constancy

Abstract: Successive color contrast and color constancy were investigated with a behavioral training technique using pigment colors. In both experiments, single, freely flying bees were trained to land on one out of 9 differently colored test fields presented on a grey background. 1. To investigate successive color contrast bees were exposed to a yellow or a blue adaptation color for several minutes and their choice behavior was tested immediately thereafter. Test fields less blue than the original training test field were chosen after adaptation to yellow, test fields of stronger blue after adaptation to blue (Fig. 2). This indicated that the ‘bee-subjective’ blue-green test fields must have appeared more blue after adaptation to yellow, and less blue after adaptation to blue. The effect lasted for about 2–3 min after adaptation durations of 1 and 2 min, and even longer after adaptation of 5 min measured for the yellow adaptation color (Fig. 3). 2. To investigate color constancy bees were trained under a ‘white’ illumination, and tested under various yellow and blue illuminations. The choice behavior revealed (Fig. 4) that under almost all conditions, the training test field was clearly preferred. This indicated that the test fields appeared in almost unchanged hues, despite the fact that the light reflected by a given test field stimulated the three receptor types in very different ratios (Fig. 5). The mean choice behavior did not change significantly during the course of a test period under colored illumination (Fig. 6). In the following test period under ‘white’ illumination, aftereffects of chromatic adaptation were observed (Fig. 7).

Contributions to the theory of invariance of color under the condition of varying illumination

Abstract: Any visual-processing algorithm aimed at attaining color constancy will in fact attain it only for restricted spectral classes of illuminants and reflectances. These classes constitute implicit heuristics for the physical world, in an artificial-intelligence sense. In the present work, physically reasonable spectral classes are presented which insure that von Kries's law of chromatic adaptation will — in its simplest form — restore object colors in human tristimulus space to illuminant-invariant positions in the space. Algebraic functions of the adapted tristimulus values are presented which are illuminant-invariant for some departures from the spectral heuristics. These functions, a hierarchy of invariants, may be useful in developing lighting and pigment standards for partially controlled viewing environments.