Number of discernible colors for color-deficient observers estimated from the MacAdam limits

Abstract

We estimated the number of colors perceived by color normal and color-deficient observers when looking at the theoretic limits of object-color stimuli. These limits, the optimal color stimuli, were computed for a color normal observer and CIE standard illuminant D65, and the resultant colors were expressed in the CIELAB and DIN99d color spaces. The corresponding color volumes for abnormal color vision were computed using models simulating for normal trichromatic observers the appearance for dichromats and anomalous trichomats. The number of colors perceived in each case was then computed from the color volumes enclosed by the optimal colors also known as MacAdam limits. It was estimated that dichromats perceive less than 1% of the colors perceived by normal trichromats and that anomalous trichromats perceive 50%-60% for anomalies in the medium-wavelength-sensitive and 60%-70% for anomalies in the long-wavelength-sensitive cones. Complementary estimates obtained similarly for the spectral locus of monochromatic stimuli suggest less impairment for color-deficient observers, a fact that is explained by the two-dimensional nature of the locus.

The Gold Standard Paradox in Digital Image Analysis: Manual Versus Automated Scoring as Ground Truth

“…29 Tremendous person-to-person variation exists for differentiating colors and color hues. 5,30 However, when people are shown different colors and color hues in isolation, recognition of differences quickly drops significantly. 31 In addition, age, certain disease states, and lifestyle choices can have an effect on the ability to see and distinguish colors.…”

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

“…The L planes were computed in the range of 10-90 in steps of 10; the planes corresponding to L 1 and L 99 were also computed. For the Rösch-MacAdam color solid, the number of discernible colors was estimated by calculating the volume because of the direct proportionality between the two quantities [17,20,22]. The convex hull volume of the Rösch-MacAdam color solid was then estimated by the MATLAB convhulln function, which is based on the Qhull algorithm [30].…”

“…To estimate the effects of the illuminants on color-deficient observers, the color volumes for abnormal color vision were computed using models simulating for normal trichromatic observers the appearance for dichromats and anomalous trichromats (for a detailed discussion of these models, see [20]). …”

“…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.…”

Robust colour constancy in red-green dichromats

“…Consequently, for practical purposes R-G dichromats only have two types of functional cones: in addition to S-cones, protanopes have operative M-cones whereas deuteranopes have operative L-cones. Given the absence of one of the pigments, colour discrimination in R-G dichromats is impaired along the R-G confusion lines [5] resulting in the perception of only a small gamut of the colours normal observers can perceive [6,7]. The famous description by John Dalton (a deuteranope himself [8]) of the pink flowers of a cranesbill, which appeared to him sky-blue by daylight but near yellow by candlelight [9], suggests that colour constancy may also be impaired in dichromacy.…”