ABSTRACT
At first pass, colour constancy occurs when one sees a thing in one’s environment to have a stable colour despite differences in the way it is illuminated at a time (simultaneous constancy) or over time (successive constancy). The phenomenon is intuitively grounded in everyday experiences in which something is partly shadowed but, in some sense, looks to be uniformly coloured (simultaneous constancy). Colour constancy is subtle phenomenon: it is situated at intersection of perceptual experience and judgement; it is influenced by myriad forces within our visual-cognitive systems; and is likely composite of interestingly disparate phenomena. One challenge is to build a colour constancy model that incorporates both the partial discounting of illumination variations via mechanisms like adaptation, and the vivid experiential impact of illumination variations familiar from shadowing and the like. The most influential “measure” of colour constancy is the Colour Constancy Index, which provides a decent measure of the extent to which what a subject identifies as matching surfaces.
