Academic journal article Psychonomic Bulletin & Review

We Infer Light in Space

Academic journal article Psychonomic Bulletin & Review

We Infer Light in Space

Article excerpt

Published online: 23 February 2013

(Q> Psychonomic Society, Inc. 2013

Abstract In studies of lightness and color constancy, the terms lightness and brightness refer to the qualia corresponding to perceived surface reflectance and perceived luminance, respectively. However, what has rarely been considered is the fact that the volume of space containing surfaces appears neither empty, void, nor black, but filled with light. Helmholtz (1866/1962) came closest to describing this phenomenon when discussing inferred illumination, but previous theoretical treatments have fallen short by restricting their considerations to the surfaces of objects. The present work is among the first to explore how we infer the light present in empty space. It concludes with several research examples supporting the theory that humans can infer the differential levels and chromaticities of illumination in three-dimensional space.

Keywords Brightness * Color constancy * Illumination * Lightness * Inferred illumination * Space perception

A complete account of color constancy requires a theory of how illumination fills three-dimensional space

Studies of lightness and color constancy use the terms lightness and brightness to refer to the qualia corresponding to perceived surface reflectance and perceived luminance, respectively (Arend & Goldstein, 1987). Missing from the literature is a consideration of how differential levels and chromaticities of the illumination that fills space are inferred (Mausfeld, 2003; Smithson, 2005). In this article, I propose that humans are aware not only of colored objects, but of the empty space around them being full of one or more levels and chromaticities of illumination. The argument is that theories of color constancy fail to grasp all of the parameters necessary to develop a broader perceptual theory, including the crucial variable of how light is inferred in open space, which has been missing from theory and, in fact, virtually all visual psychophysics.

The problem with collapsing a three-dimensional world into two dimensions

Color theory has been developed to explain the perception of isolated spots of light and their appearance, as, for exam- ple, by trichromacy and opponency. When lights are surrounded by other chromatic stimuli, further effects- such as color contrast and color constancy-have been studied. In all cases, the spots and surrounds are presented on a flat surface (e.g., "object mode") or as an opening into a flat surface (e.g., "aperture mode"). Such methods do not easily lend themselves to inferences about the volumetric qualities of space, since any such properties will be identical for both the spot and the surround. Nevertheless, many authors have presupposed that color vision can be complete- ly described by the perceptions of spots and surrounds on flat surfaces. One can trace this attitude back to the perspec- tive reduction discovered in the Renaissance, which seemed to imply that all volumetric information can be represented in two dimensions by a painter.

The famous painter Alberti (1435) was the first to design a two-dimensional pane of glass that could represent a scene in three-dimensional perspective. Mausfeld (2002) discussed how Alberti's window, capitalizing on this geometrical advance, contains all of the primitives necessary for the representation of both lower- and higher-order color processes. "Lower" pro- cesses contain elementary achievements, including color matching, color discrimination, and their temporal and spatial properties, while "higher" processes designate functional per- spectives and focus on achievements such as color constancy. While Mausfeld does not consider "lower" to imply retinal versus "higher" cortical processes, as in Land and McCann's (1971) Retinex model, Mausfeld does follow the traditional assumption that decontextual colors (represented in CIE space as hue, saturation, and brightness) are the elemental compo- nents used by higher-order processes, such as those that evoke color constancy. …

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