Effects of Illuminant chromaticity on color constancy

摘要

Past research on color constancy has mainly focused on surfaces illuminated by a restricted set of illuminants. Since other visual functions related to color, such as color discrimination, exhibit systematic variations with hue, we wanted to investigate whether there are systematic differences in the degree of color constancy between illuminants of varying hues. We varied chromaticity and saturation of the illuminant in rendered two- and three-dimensional scenes displayed on a LCD screen extending a visual angle of 58.9?° x 38.9?°. The scenes depicted different versions of an illusion introduced by Lotto & Purves (2004). Ten na?ˉve observers performed achromatic matches on scenes illuminated by illuminants of 20 different chromaticities and two saturation levels. The surface reflectances were chosen from the axes of DKL-Color-space, rotated in steps of 18?° azimuth in accordance with the illuminants. Each Illuminant was chosen so that it exactly canceled the chromaticity of one of the surface colors used. Observers had to adjust a central patch in the scene until it appeared achromatic to them. Color constancy was defined as the magnitude of the correction observers used to adjust a gray, relative to the shift of the neutral patch under that illuminant. We observed levels of color constancy between 25% and 75% for different observers and conditions. There were only small differences between 2D- and 3D scenes and for the two different saturation levels. There was a trend towards higher constancy for illuminants varying in color directions close to the daylight locus. Overall, color constancy seems to be fairly stable across different illuminant directions. Lotto RB, Purves D (2004) Perceiving Colour. Review of Progress in Coloration 34: 12-25.