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

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.

This work was supported by the Spanish Ministry for Education and Science (DPI2005-08999-C02-02); the Spanish Ministry of Science and Innovation (DPI2008-06455-C02-02); the Centro de Física at Minho University, Braga, Portugal and the Portuguese Fundação para a Ciência e a Tecnologia (PTDC/EEA-EEL/098572/2008). Esther Perales was supported by the Spanish Ministry for Education and Science with the BES-2006-13518 grant, and João M. M. Linhares was supported by the Portuguese Fundação para a Ciência e a Tecnologia with the SFRH/BD/35874/ grant.