Article

Brightness and darkness as perceptual dimensions.

Laboratory of Experimental Ophthalmology & BCN NeuroImaging Centre, School of Behavioural and Cognitive Neurosciences, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
PLoS Computational Biology (Impact Factor: 4.87). 11/2007; 3(10):e179. DOI: 10.1371/journal.pcbi.0030179
Source: PubMed

ABSTRACT A common-sense assumption concerning visual perception states that brightness and darkness cannot coexist at a given spatial location. One corollary of this assumption is that achromatic colors, or perceived grey shades, are contained in a one-dimensional (1-D) space varying from bright to dark. The results of many previous psychophysical studies suggest, by contrast, that achromatic colors are represented as points in a color space composed of two or more perceptual dimensions. The nature of these perceptual dimensions, however, presently remains unclear. Here we provide direct evidence that brightness and darkness form the dimensions of a two-dimensional (2-D) achromatic color space. This color space may play a role in the representation of object surfaces viewed against natural backgrounds, which simultaneously induce both brightness and darkness signals. Our 2-D model generalizes to the chromatic dimensions of color perception, indicating that redness and greenness (blueness and yellowness) also form perceptual dimensions. Collectively, these findings suggest that human color space is composed of six dimensions, rather than the conventional three.

0 Bookmarks
 · 
121 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Simultaneous contrast refers to the respective whitening or blackening of physically identical image regions surrounded by regions of low or high luminance, respectively. A common method of measuring the strength of this effect is achromatic color matching, in which subjects adjust the luminance of a target region to achieve an achromatic color match with another region. Here I present psychophysical data questioning the assumption-built into many models of achromatic color perception-that achromatic colors are represented as points in a one-dimensional (1D) perceptual space, or an absolute achromatic color gamut. I present an alternative model in which the achromatic color gamut corresponding to a target region is defined relatively, with respect to surround luminance. Different achromatic color gamuts in this model correspond to different 1D lines through a 2D perceptual space composed of blackness and whiteness dimensions. Each such line represents a unique gamut of achromatic colors ranging from black to white. I term this concept gamut relativity. Achromatic color matches made between targets surrounded by regions of different luminance are shown to reflect the relative perceptual distances between points lying on different gamut lines. The model suggests a novel geometrical approach to simultaneous contrast and achromatic color matching in terms of the vector summation of local luminance and contrast components, and sets the stage for a unified computational theory of achromatic color perception.
    Vision research 08/2012; 69:49-63. · 2.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Classical approaches to transparency perception assume that transparency constitutes a perceptual dimension corresponding to the physical dimension of transmittance. Here I present an alternative theory, termed gamut relativity, that naturally explains key aspects of transparency perception. Rather than being computed as values along a perceptual dimension corresponding to transmittance, gamut relativity postulates that transparency is built directly into the fabric of the visual system's representation of surface color. The theory, originally developed to explain properties of brightness and lightness perception, proposes how the relativity of the achromatic color gamut in a perceptual blackness-whiteness space underlies the representation of foreground and background surface layers. Whereas brightness and lightness perception were previously reanalyzed in terms of the relativity of the achromatic color gamut with respect to illumination level, transparency perception is here reinterpreted in terms of relativity with respect to physical transmittance. The relativity of the achromatic color gamut thus emerges as a fundamental computational principle underlying surface perception. A duality theorem relates the definition of transparency provided in gamut relativity with the classical definition underlying the physical blending models of computer graphics.
    Journal of the Optical Society of America A 03/2013; 30(3):418-26. · 1.67 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Brill and Carter [Color Res Appl (DOI:10.1002/col21777)] rekindle the question of whether brightness scaling is better approximated by a log or power function, proposing on theoretical and empirical grounds that the log function is the correct choice. This note provides a new twist to this debate in terms of a recently introduced theory of brightness and lightness per-ception, called gamut relativity. The theory reconciles the log and power function formulations and approximately predicts the weight/exponent values associated with these functions. The theory provides, moreover, a unified and testable approach to human performance in brightness magnitude estimation, discrimination and matching tasks.
    Color Research & Application 11/2013; · 1.01 Impact Factor

Full-text (2 Sources)

View
66 Downloads
Available from
May 30, 2014