Abstract
Previous studies suggest that to achieve color constancy, the human visual system makes use of multiple cues, including a priori assumptions about the illumination (“daylight priors”). Specular highlights have been proposed to aid constancy, but the evidence for their usefulness is mixed. Here, we used a novel cue-combination approach to test whether the presence of specular highlights or the validity of a daylight prior improves illumination chromaticity estimates, inferred from achromatic settings, to determine whether and under which conditions either cue contributes to color constancy. Observers made achromatic settings within three-dimensional rendered scenes containing matte or glossy shapes, illuminated by either daylight or nondaylight illuminations. We assessed both the variability of these settings and their accuracy, in terms of the standard color constancy index (CCI). When a spectrally uniform background was present, neither CCIs nor variability improved with specular highlights or daylight illuminants (Experiment 1). When a Mondrian background was introduced, CCIs decreased overall but were higher for scenes containing glossy, as opposed to matte, shapes (Experiments 2 and 3). There was no overall reduction in variability of settings and no benefit for scenes illuminated by daylights. Taken together, these results suggest that the human visual system indeed uses specular highlights to improve color constancy but only when other cues, such as from the local surround, are weakened.
Highlights
General overviewObservers generally have little difficulty judging objects as having a relatively stable color under changesCitation: Wedge-Roberts, R., Aston, S., Beierholm, U., Kentridge, R., Hurlbert, A., Nardini, M., & Olkkonen, M. (2020)
We investigated whether judgments are less variable and more accurate along the daylight locus, consistent with the use of daylight priors, and whether these would interact with specular highlights
The fact that raw settings are still drawn toward the blue illumination chromaticity suggests that this is not caused by the local surround of the central shape, which previously always had the same surface reflectance but here averages out to a neutral chromaticity. This series of experiments was designed to test three primary hypotheses: that specular highlights would improve color constancy and decrease variable error, that the effect of highlights would be mediated by the type of illumination and position of a matching patch, and that scenes illuminated by daylights would result in a higher degree of color constancy than scenes illuminated by nondaylights
Summary
Observers generally have little difficulty judging objects as having a relatively stable color under changes. Received February 28, 2020; published November 10, 2020. It is still unknown to what extent they are able to make use of specular highlights to assist in this. In this series of experiments, we tested whether observers’ color constancy improves when specular highlights are present. We investigated whether judgments are less variable and more accurate along the daylight locus, consistent with the use of daylight priors, and whether these would interact with specular highlights
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
