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16
Color Constancy: Generalized Diagonal Transforms Suffice
 J. Opt. Soc. Am. A
, 1994
"... This study's main result is to show that under the conditions imposed by the MaloneyWandell color constancy algorithm, whereby illuminants are three dimensional and reflectances two dimensional (the 32 world), color constancy can be expressed in terms of a simple independent adjustment of the ..."
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Cited by 102 (24 self)
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This study's main result is to show that under the conditions imposed by the MaloneyWandell color constancy algorithm, whereby illuminants are three dimensional and reflectances two dimensional (the 32 world), color constancy can be expressed in terms of a simple independent adjustment of the sensor responses (in other words, as a von Kries adaptation type of coefficient rule algorithm) as long as the sensor space is first transformed to a new basis. A consequence of this result is that any color constancy algorithm that makes 32 assumptions, such as the MaloneyWandell subspace algorithm, Forsyth's MWEXT, and the FuntDrew lightness algorithm, must effectively calculate a simple von Kriestype scaling of sensor responses, i.e., a diagonal matrix. Our results are strong in the sense that no constraint is placed on the initial spectral sensitivities of the sensors. In addition to purely theoretical arguments, we present results from simulations of von Kriestype color constancy in which the spectra of real illuminants and reflectances along with the humanconesensitivity functions are used. The simulations demonstrate that when the cone sensor space is transformed to its new basis in the appropriate manner a diagonal matrix supports nearly optimal color constancy. Key words: color constancy, von Kries, chromatic adaptation, color balancing. 1.
Diagonal transforms suffice for color constancy.
 4th International Conference on Computer Vision. (IEEE 402 Computer
, 1993
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Performance of a Chromatic Adaption Transform based on Spectral Sharpening
"... The Bradford chromatic adaptation transform, empirically derived by Lam, models illumination change. Specifically, it provides a means of mapping XYZs under a reference light source to XYZs for a target light source such that the corresponding XYZs produce the same perceived color. ..."
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Cited by 15 (6 self)
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The Bradford chromatic adaptation transform, empirically derived by Lam, models illumination change. Specifically, it provides a means of mapping XYZs under a reference light source to XYZs for a target light source such that the corresponding XYZs produce the same perceived color.
Aberrationfree measurements of the visibility of isoluminant gratings
 Journal of the Optical Society of America (A
, 1993
"... We developed a new apparatus and psychophysical technique to extend isoluminant contrastsensitivity measurements to high spatial frequencies. The apparatus consists of two identical laser interferometers that are designed to produce phaselocked twocolor interference fringes on the retina without ..."
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Cited by 13 (2 self)
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We developed a new apparatus and psychophysical technique to extend isoluminant contrastsensitivity measurements to high spatial frequencies. The apparatus consists of two identical laser interferometers that are designed to produce phaselocked twocolor interference fringes on the retina without the influence of diffraction and most aberrations in the eye. However, even with interferometry, transverse chromatic aberration of the eye can produce a wavelengthdependent phase shift in the interference fringes, which can be exaggerated by head movements. To reduce the effect of head movements, isoluminant red and green interference fringes of equal spatial frequency and orientation were drifted slowly in opposite directions to guarantee a purely isochromatic (in phase) and a purely isoluminant (out of phase) stimulus during each cycle of stimulus presentation. With this technique we found that observers could resolve red and green stripes at spatial frequencies higher than 20 cycles per degree (c/deg) (2027 c/deg), substantially higher than has previously been reported. This places a lower bound on the sampling density of neurons that mediate color vision. At all spatial frequencies, even those above the isoluminant resolution limit, a relative phase of the red and the green components could be found that obliterated the appearance of luminance modulation at the fringe frequency. Above the resolution limit, redgreenisoluminant interference fringes are seen as spatial noise, which may be chromatic aliasing caused by spatial sampling at some stage in the chromatic pathway.
Coefficient Color Constancy
, 1995
"... The goal of color constancy is to take the color responses (for example camera rgb triplets) of surfaces viewed under an unknown illuminant and map them to illuminant independent descriptors. In existing theories this mapping is either a general linear 3 x 3 matrix or a simple diagonal matrix of sca ..."
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Cited by 10 (1 self)
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The goal of color constancy is to take the color responses (for example camera rgb triplets) of surfaces viewed under an unknown illuminant and map them to illuminant independent descriptors. In existing theories this mapping is either a general linear 3 x 3 matrix or a simple diagonal matrix of scaling coefficients. The general theories have the advantage that the illuminant can be accurately discounted but have the disadvantage that nine parameters must be recovered. Conversely while the coefficient theories have only three unknowns, a diagonal matrix may only partially discount the illuminant. My staring point in this thesis is to generalize the coefficient approach; the goal is to retain its inherent simplicity while at the same time increasing its expressive power. Under the generalized coefficient scheme, I propose that a visual system transforms responses to a new sensor basis before applying the scaling coefficients. I present methods for choosing the best coefficient bas...
Color constancy: Enhancing von Kries adaptation via sensor transformation, SPIE
, 1993
"... Von Kries adaptation has long been considered a reasonable vehicle for color constancy. Since the color constancy performance attainable via the von Kries rule strongly depends on the spectral response characteristics of the human cones, we consider the possibility of enhancing von Kries performance ..."
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Cited by 5 (2 self)
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Von Kries adaptation has long been considered a reasonable vehicle for color constancy. Since the color constancy performance attainable via the von Kries rule strongly depends on the spectral response characteristics of the human cones, we consider the possibility of enhancing von Kries performance by constructing new &quot;sensors &quot; as linear combinations of the fixed cone sensitivity functions. We show that if surface refiectances are wellmodeled by 3 basis functions and illuminants by 2 basis functions then there exists a set of new sensors for which von Kries adaptation can yield perfect color constancy. These new sensors can (like the cones) be described as long, medium, and shortwave sensitive; however, both the new long and mediumwave sensors have sharpened sensitivities—their support is more concentrated. The new shortwave sensor remains relatively unchanged. A similar sharpening of cone sensitivities has previously been observed in test and field spectral sensitivities measured for the human eye. We present simulation results demonstrating improved von Kries performance using the new sensors even when the restrictions on the illumination and reflectance are relaxed. 1
Spectral Sharpening and the Bradford Transform
 Proc. CIS2000
, 2000
"... The Bradford chromatic adaptation transform, empirically derived by Lam [1], models illumination change. Specifically, it provides a means of mapping XYZs under a reference source to XYZs for a target light such that the corresponding XYZs produce the same perceived colour. ..."
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Cited by 4 (1 self)
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The Bradford chromatic adaptation transform, empirically derived by Lam [1], models illumination change. Specifically, it provides a means of mapping XYZs under a reference source to XYZs for a target light such that the corresponding XYZs produce the same perceived colour.
The Foundations of Color Measurement and Color Perception
 SID SEMINAR LECTURE NOTES
, 1996
"... This tutorial is an introductory review of color science. The logical and experimental basis of the CIE standard observer and standard observer tools are emphasized. In addition, some aspects of devicecalibration are discussed. Finally, the shortcomings of the CIE standard observer are reviewed in ..."
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Cited by 4 (3 self)
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This tutorial is an introductory review of color science. The logical and experimental basis of the CIE standard observer and standard observer tools are emphasized. In addition, some aspects of devicecalibration are discussed. Finally, the shortcomings of the CIE standard observer are reviewed in order to ready the student for the more advanced tutorials on color appearance.
Color Ratios and Chromatic Adaptation
 Proc. IS&T CGIV
, 2002
"... In this paper, the performance of chromatic adaptation transforms based on stable color ratios is investigated. It was found that for three different sets of reflectance data, their performance was not statistically different from CMCCAT2000, when applying the chromatic adaptation transforms to Lam& ..."
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Cited by 3 (1 self)
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In this paper, the performance of chromatic adaptation transforms based on stable color ratios is investigated. It was found that for three different sets of reflectance data, their performance was not statistically different from CMCCAT2000, when applying the chromatic adaptation transforms to Lam's corresponding color data set and using a perceptual error metric of CIE AE94. The sensors with the best color ratio stability are much sharper and more decorrelated than the CMCCAT2000 sensors, corresponding better to sensor responses found in other psychovisual studies. The new sensors also closely match those used by the sharp adaptation transform Keywords Spherical Sampling, Optimization, Color constancy, Color ratio stability, Chromatic Adaptation Transforms (CATs), CMCCAT2000.