Hue, saturation, and lightness of surface colors with chromatic illumination

Abstract

The visual mechanism of a normal observer is so constructed that objects keep nearly their daylight colors even when the illuminant departs markedly from average daylight. The processes by m eans of which t he observer becomes adapted to the illuminant or discounts most of the effect of a nondaylight illuminant are complicated; they are known to be partly retinal and partly cortical. By taking into account the various fragments of both qualitative and quantitative information to be found in the literature, relations have been formulated by means of which it is possible to compute approximately the hue, saturation , and lightness (tint, value) of a surface color from the tristimulus specifi cations of the light reflected from the surface and of the light reflected from the background against which it is viewed. Prelimin ary observations of 15 surfaces under each of 5 different illumina nts have demonstrated the adequacy of the formulation, and have led to an approximate evaluation of the constants appearing in it. More detailed and extensive observations have been carried out in the psychological laboratories of Bryn Mawr College, and these observations have resulted in an improved formulation.

Essay Concerning Color Constancy

“…That is, the measured changes in proportions of the matching lights vary systematically with the luminance level of the test field relative to the surround luminance to which the eye is adapted. The departures from the proportionality rule are, moreover, in the directions that would have been predicted from a nonconstancy phenomenon known as the Helson-Judd effect (Helson 1938;Judd 1940). Spectrally nonselective surfaces seen against a spectrally nonselective background all appear achromatic (white through grays to black) in white light.…”

Quantitative evaluation of internal marks made using MRgFUS as seen on MRI, CT, US, and digital color images – A pilot study

“…For this study, conspicuity was defined using the International Commission on Illumination (CIE) L*u*v* color space (CIELUV) criteria, ΔE established for distinguishing color [19]. Briefly, red/green/blue color values can be converted to the LUV colorspace, and the value ΔE can be calculated describing quantitatively how well a sample color matches a reference color.…”

Chromatic adaptation and colour constancy

“…Although there is poor experimental support for the von Kries coeffi cient law, its use persists as a rough approximation to the general trend of adaptation-induced colour shifts due to simplicity. Judd (1940) proposed discounting the colour of the illuminant due to adaptation by subtracting tristimulus values of a reference white from those of the object colour (Equation [6.2]):…”