Abstract
Color constancy is the ability to recover a stable perceptual estimate of surface reflectance, regardless of the lighting environment. However, we know little about how observers make judgments of the surface color of glossy objects, particularly in complex lighting environments that introduce complex spatial patterns of chromatic variation across an object’s surface. To address this question, we measured thresholds for reflectance discrimination using computer-rendered stimuli under environmental illumination. In Experiment 1, we found that glossiness and shape had small effects on discrimination thresholds. Importantly, discrimination ellipses extended along the direction in which the chromaticities in the environmental illumination spread. In Experiment 2, we also found that the observers’ abilities to judge surface colors were worse in lighting environments with an atypical chromatic distribution.
Highlights
Color constancy is the visual ability that allows us to judge the surface colors of objects under various lighting environments
Environmental variation in incident illumination expands the gamut of chromaticities contained in the diffuse component of the proximal image of the object [Fig. 1(b)]. In addition to this variation in the diffuse component, the full variation of chromaticities in environmental illumination is carried unmodified in the specular component [Fig. 1(c)]
For a perfectly color-constant observer, the type of illumination should not affect the thresholds for reflectance discrimination
Summary
Color constancy is the visual ability that allows us to judge the surface colors of objects under various lighting environments. The visual system needs to cancel the influence of illumination and retrieve an estimate of surface color Such a separation is an under-constrained problem because we typically have access to only the cone signals elicited by the illumination once it has been spectrally modified by surface spectral reflectance. One of the limitations of past studies is the use of simplified stimuli where objects were typically two-dimensional (2D), matte and uniformly illuminated by a single light source [2,3]. Such stimuli allow careful experimental control, they lack some of the important features of surfaces and illuminants that potentially offer cues for color constancy. Color constancy for glossy objects may be supported by some additional mechanisms that are not available for matte stimuli
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