Master thesis: Extensions of a linear model of surface reflectance

Philipona O’Regan recently proposed a linear model of surface reflectance asit is sensed by the human eyes. In their model, the three dimensional cone response to reflected light is accurately approximated by a linear transformation of the three dimensional response to illumination. The geometrical properties of this linear transformation, such as singularity, correlate with psychophysical results on focal colors and unique hues. Later, Vazquez-Corral et al. built a bridge between Philipona & O’Regan’s model and von Kries-like approaches to color constancy in computer vision by showing that the linear operators could be diagonalized in a common basis. However both of these studies required specifyinga particular dataset of illuminants. We will show in this paper that it is possible to compute adequate linear operators and a common basis for diagonalization without specifying any particular set of illuminants, thus enhancing their generalizability to illuminant changes, while maintaining correlations with features of the human color vision. Further analysis of the characteristics of singularity in reflection properties will also be presented.

Social Perception of Facial Color Appearance for Human Trichromatic Versus Dichromatic Color Vision

Typical human color vision is trichromatic, on the basis that we have three distinct classes of photoreceptors. A recent evolutionary account posits that trichromacy facilitates detecting subtle skin color changes to better distinguish important social states related to proceptivity, health, and emotion in others. Across two experiments, we manipulated the facial color appearance of images consistent with a skin blood perfusion response and asked participants to evaluate the perceived attractiveness, health, and anger of the face (trichromatic condition). We additionally simulated what these faces would look like for three dichromatic conditions (protanopia, deuteranopia, tritanopia). The results demonstrated that flushed (relative to baseline) faces were perceived as more attractive, healthy, and angry in the trichromatic and tritanopia conditions, but not in the protanopia and deuteranopia conditions. The results provide empirical support for the social perception account of trichromatic color vision evolution and lead to systematic predictions of social perception based on ecological social perception theory.