Linear programming method for computing the gamut of object color solid

Technological innovation in all areas has led to the appearance in recent years of new metallic and pearlescent materials, yet no exhaustive studies have been conducted to assess their colorimetric capabilities. The chromatic variability of these special-effect pigments may largely be due to the three-dimensional effect of their curved shapes and orientations when they are directionally or diffusely illuminated. Our study examines goniochromatic colors using the optimal colors (MacAdam limits) associated with normal colors (photometric scale of relative spectral reflectance from 0 to 1) under certain conventional illuminants and other light sources. From a database of 91 metallic and interference samples and using a multigonio-spectrophotometer, we analyzed samples with lightness values of more than 100 and others with lightness values of less than 100, but with higher chromaticities than optimal colors, which places them beyond the MacAdam limits. Our study thus demonstrates the existence of chromatic perceptions beyond the normal solid color associated with these materials and independent of the light source. The challenge for future research, therefore, is to replicate and render these color appearances in current and future color reproduction technologies for computer graphics.

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“…Therefore, the color solid associated with the CIE 1931 standard observer and different illuminants, was calculated [21,22] …”

Section: Methodsmentioning

confidence: 99%

Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources

Perales

Chorro

Cramer³

et al. 2011

Appl. Opt.

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“…It took about 1 h for each optimal-color type and lightness. In the method of Li et al [31], the algorithm finds reflectance values at intervals of 1 nm instead of 0.1 nm. The computational cost is less than that of Martínez-Verdú et al's method; it took several minutes to obtain a locus.…”

Section: A Optimal-color Computationmentioning

confidence: 99%

Number of discernible object colors is a conundrum

Masaoka¹,

Berns

Fairchild

et al. 2013

J. Opt. Soc. Am. A

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Widely varying estimates of the number of discernible object colors have been made by using various methods over the past 100 years. To clarify the source of the discrepancies in the previous, inconsistent estimates, the number of discernible object colors is estimated over a wide range of color temperatures and illuminance levels using several chromatic adaptation models, color spaces, and color difference limens. Efficient and accurate models are used to compute optimal-color solids and count the number of discernible colors. A comprehensive simulation reveals limitations in the ability of current color appearance models to estimate the number of discernible colors even if the color solid is smaller than the optimal-color solid. The estimates depend on the color appearance model, color space, and color difference limen used. The fundamental problem lies in the von Kries-type chromatic adaptation transforms, which have an unknown effect on the ranking of the number of discernible colors at different color temperatures.

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“…The optimal colors under each illuminant were obtained by the method proposed by Li et al [19]. The method consists of a linear programming approach and was preferred in relation to other more complex methods [17] due to its reduced computation time, an important requirement in the optimization procedure applied here.…”

Section: B Optimal Colors and Rösch-macadam Volumesmentioning

confidence: 99%

“…The optimal colors represent the theoretical limits of all colors arising only by reflection (or transmission) [12], and the corresponding loci was computed in a color diagram [13,14] and was recalculated later by MacAdam [15,16] to obtain the MacAdam limits or Rösch-MacAdam limits. The Rösch-MacAdam solid expressed in the CIELAB color space is a powerful tool and has been routinely used to estimate the color rendering capability of daylight and of standard illuminants [17][18][19], the gamut of color-deficient observers [20], and the theoretical limits of the number of distinguishable colors [21,22]. The strength of this approach to evaluate the extent of discrimination is its generality, since it does not require the use of a set of samples or of a reference illuminant for the calculations.…”

Section: Introductionmentioning

confidence: 99%

Effects of high-color-discrimination capability spectra on color-deficient vision

et al. 2013

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Light sources with three spectral bands in specific spectral positions are known to have high-color-discrimination capability. W. A. Thornton hypothesized that they may also enhance color discrimination for color-deficient observers. This hypothesis was tested here by comparing the Rösch-MacAdam color volume for color-deficient observers rendered by three of these singular spectra, two reported previously and one derived in this paper by maximization of the Rösch-MacAdam color solid. It was found that all illuminants tested enhance discriminability for deuteranomalous observers, but their impact on other congenital deficiencies was variable. The best illuminant was the one derived here, as it was clearly advantageous for the two red-green anomalies and for tritanopes and almost neutral for red-green dichromats. We conclude that three-band spectra with high-colordiscrimination capability for normal observers do not necessarily produce comparable enhancements for color-deficient observers, but suitable spectral optimization clearly enhances the vision of the color deficient.

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Linear programming method for computing the gamut of object color solid

Cited by 7 publications

References 10 publications

Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources

Analysis of the colorimetric properties of goniochromatic colors using the MacAdam limits under different light sources

Number of discernible object colors is a conundrum

Effects of high-color-discrimination capability spectra on color-deficient vision

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