Spectral Hue as a Function of Intensity

Purdy, D. M.

doi:10.2307/1415157

Cited by 160 publications

(51 citation statements)

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“…Our main points agree with some findings of Purdy (1931). He found that equilibrium green is invariant with luminance and coincides with an invariant wavelength for the Bezold-Briicke shift.…”

Section: Eqcillbrlasupporting

confidence: 92%

Opponent process additivity—II. Yellow/blue equilibria and nonlinear models

1975

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Abstract-A yellow/blue equilibrium Iight is one which appears neither yellowish nor bluish (i.e. uniquely red, uniquely green, or achromatic). The spectral locus of the monochromatic greenish equilibrium (around 500 nm) shows little, if any, variation over a luminance range of .! log,, units. Reddish equilibria are extraspectral. involving mixtures of short-and long-wave light. Their wavelength composition is noninvariant with luminance: a reddish equilibrium light turns bluish-red if luminance is increased with wavelength composition constant.The additive mixture of the reddish and greenish equilibria is again a yellow, blue equilibrium light.We conclude that yellow/blue equilibrium can be described as the zeroing of a nonlinear functional.which is, however, approximately linear in the short-wavelength ("blue") and middle-wavelength ("green") cone responsesand nonlinear only in the long-wavelength ("red") cone response. The "red" cones contribute to yellowness but via a compressive function of luminance. This effect works against the direction of the Bezold-Briicke hue shift. The Jameson-Hurvich yellowiblue chromatic-response function is only approximately correct; the relative values of yellow/blue chromatic response for an equal energy spectrum must vary somewhat with the energy level.

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Section: Eqcillbrlasupporting

confidence: 92%

Opponent process additivity—II. Yellow/blue equilibria and nonlinear models

1975

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“…Some evidence for closure property (i) is provided by the invariance of unique hues with respect to the Bezold-Briicke shift (Purdy, 1931). But there have been hardly any tests of(i) for nonspectral lights, nor has (ii) been tested directly.…”

Section: Introductionmentioning

confidence: 99%

Opponent-process additivity-I: Red/green equilibria

1974

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Abstract-A red/green equilibrium light is one which appears neither reddish nor greenish (i.e. either uniquely yellow, uniquely blue, or achromatic). A subset of spectral and nonspectral red/green equilibria was determined for several luminance levels, in order to test whether the set of all such equilibria is closed under linear color-mixture operations.The spectral loci ofequilibrium yellow and blue showedeither no variation or visually insignificant variation over a range of l-2 log,, unit. There were no trends that were repeatable across observers. We concluded that spectral red/green equilibria are closed under scalar multiplication; consequently they are invariant hues relative to the Bezold-Briicke shift.The additive mixture of yellow and blue equilibrium wavelengths, in any luminance ratio, is also an equilibrium light. Small changes of the yellowish component of a mixture toward redness or greeness must be compensated by predictable changes of the bluish component of the mixture toward greenness or redness. We concluded that yellow and blue equilibria are complementary relative to an equilibrium white; that desaturation of a yellow or blue equilibrium light with such a white produces no Abney hue shift; and that the set of red/green equilibria is closed under general linear operations. One consequence is that the red/green chromatic-response function, measured by the Jameson-Hurvich technique of cancellation to equilibrium, is a linear function of the individual's color-matching coordinates. A second consequence of linear closure of equilibria is a strong constraint on the class of combination rules by which receptor outputs are recoded into the red/green opponent process.

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“…Although color percepts are obviously initiated by the spectral characteristics of light stimuli, a major difficulty rationalizing these color qualities in either neurobiological or psychological terms is that they are not linked in any straightforward way to the physical attributes of the corresponding retinal stimuli (i.e., to the energy distribution in the stimuli, to their relative uniformity, or to their overall power, respectively). Thus varying the physical parameter underlying any one of these perceptual categories changes the appearance of all three qualities in highly nonlinear and interdependent ways (1)(2)(3)(4)(5)(6)(7)(8) .…”

mentioning

confidence: 99%

“…In color-matching tests, (i) saturation varies as a function of luminance [the Hunt effect (3)]; (ii) hue varies as a function of stimulus changes that affect saturation [the Abney effect (4, 5)]; (iii) hue varies as a function of luminance [the Bezold-Brücke effect (6, 7)]; and (iv) brightness varies as a function of stimulus changes that affect both hue and saturation [the Helmholtz-Kohlrausch effect (8)] . Explanations proposed in the past have been based on assumptions about neuronal interactions early in the visual pathway and have not led to any consensus (3,6,(8)(9)(10)(11).…”

mentioning

confidence: 99%

Spectral statistics in natural scenes predict hue, saturation, and brightness

Long

Yang

Purves

2006

Proc. Natl. Acad. Sci. U.S.A.

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The perceptual color qualities of hue, saturation, and brightness do not correspond in any simple way to the physical characteristics of retinal stimuli, a fact that poses a major obstacle for any explanation of color vision. Here we test the hypothesis that these basic color attributes are determined by the statistical covariations in the spectral stimuli that humans have always experienced in typical visual environments. Using a database of 1,600 natural images, we analyzed the joint probability distributions of the physical variables most relevant to each of these perceptual qualities. The cumulative density functions derived from these distributions predict the major colorimetric functions that have been reported in psychophysical experiments over the last century.color ͉ colorimetry ͉ perception ͉ psychophysics ͉ vision C olor percepts are described in terms of hue (the sensation of the relative redness, greenness, blueness, or yellowness of a spectral stimulus), saturation (the degree to which a color percept deviates from neutral gray), and brightness (the apparent intensity of the stimulus). Although color percepts are obviously initiated by the spectral characteristics of light stimuli, a major difficulty rationalizing these color qualities in either neurobiological or psychological terms is that they are not linked in any straightforward way to the physical attributes of the corresponding retinal stimuli (i.e., to the energy distribution in the stimuli, to their relative uniformity, or to their overall power, respectively). Thus varying the physical parameter underlying any one of these perceptual categories changes the appearance of all three qualities in highly nonlinear and interdependent ways (1-8) .These classical psychophysical functions, which are illustrated in the Figs. 1a-6a, can be divided into those measured by color discrimination testing and those revealed in color-matching paradigms. In color discrimination tests, the ability to distinguish equally noticeable (or just noticeable) differences in hue or saturation varies systematically as a function of the wavelength of a monochromatic stimulus (1, 2). In color-matching tests, (i) saturation varies as a function of luminance [the Hunt effect (3) Motivated by evidence that natural image statistics predict the response properties of some visual neurons (12) and that imagesource statistics predict several aspects of visual perception (13-16), we here examine the hypothesis that this perplexing phenomenology arises from a scheme of visual processing based on statistical covariations of the physical characteristics of light stimuli in typical visual environments. To test this possibility, we acquired a database of 1,600 color images of natural scenes to approximate the range of light stimuli that humans have normally witnessed (see Fig. 7, which is published as supporting information on the PNAS web site). The joint probability distributions of the physical correlates most closely associated with hue, saturation, and brightness were then analyz...

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Spectral Hue as a Function of Intensity

Cited by 160 publications

References 0 publications

Opponent process additivity—II. Yellow/blue equilibria and nonlinear models

Opponent process additivity—II. Yellow/blue equilibria and nonlinear models

Opponent-process additivity-I: Red/green equilibria

Spectral statistics in natural scenes predict hue, saturation, and brightness

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