Rethinking Colour Constancy

Abstract

Colour constancy needs to be reconsidered in light of the limits imposed by metamer mismatching. Metamer mismatching refers to the fact that two objects reflecting metameric light under one illumination may reflect non-metameric light under a second; so two objects appearing as having the same colour under one illuminant can appear as having different colours under a second. Yet since Helmholtz, object colour has generally been believed to remain relatively constant. The deviations from colour constancy registered in experiments are usually thought to be small enough that they do not contradict the notion of colour constancy. However, it is important to determine how the deviations from colour constancy relate to the limits metamer mismatching imposes on constancy. Hence, we calculated metamer mismatching’s effect for the 20 Munsell papers and 8 pairs of illuminants employed in the colour constancy study by Logvinenko and Tokunaga and found it to be so extensive that the two notions—metamer mismatching and colour constancy—must be mutually exclusive. In particular, the notion of colour constancy leads to some paradoxical phenomena such as the possibility of 20 objects having the same colour under chromatic light dispersing into a hue circle of colours under neutral light. Thus, colour constancy refers to a phenomenon, which because of metamer mismatching, simply cannot exist. Moreover, it obscures the really important visual phenomenon; namely, the alteration of object colours induced by illumination change. We show that colour is not an independent, intrinsic attribute of an object, but rather an attribute of an object/light pair, and then define a concept of material colour in terms of equivalence classes of such object/light pairs. We suggest that studying the shift in material colour under a change in illuminant will be more fruitful than pursuing colour constancy’s false premise that colour is an intrinsic attribute of an object.

Master thesis: Extensions of a linear model of surface reflectance

“…Color constancy has been extensively studied in human as well as in computer vision, and remains the subject of debate (Logvinenko et al 2015). Many theories and approaches to color constancy attempt to estimate the illuminant from the visual scene (Land 1964;Van De Weijer and Gevers 2005;Provenzi et al 2008), and then discount it from the AI.…”

Computational color prediction versus least-dissimilar matching

“…As L&T point out, a perfect asymmetric match will usually be impossible due to metamer mismatching (i.e., the fact that two different reflectances may reflect metameric lights under one illuminant, but non-metameric lights under a second illuminant). Further analysis of the effect of metamer mismatching in the context of this experiment is provided by Logvinenko et al [7].…”

“…Derhak and Berns define the goal of a MAT as "…to predict material constancy or how sensor excitations for an object color change with changes in observing conditions" [10]. The problem with this definition is, as established by Logvinenko et al [7], that as a result of metamer mismatching intrinsic object colors that are independent of the illuminant simply do not exist-hence material constancy in the Derhak and Berns sense does not exist either, since from such material constancy intrinsic object color would immediately follow.…”

Colorizing Color Images

“…Another term for white balancing in the context of digital images is color constancy. Hence the proposed method also addresses the color constancy problem; however, we avoid further use of that term since Logvinenko et al [5] proved that color constancy defined as the determination of the intrinsic color of surfaces from trichromatic data simply does not exist in principle. Our 'color constancy' goal, therefore, is not to extract intrinsic surface properties but rather to remove color casts from images.…”