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R.C. Baraas, D.H. Foster, K. Amano, S.M. C. Nascimento; Ability of Anomalous Trichromats to Judge Natural and Munsell Surface Colors Under Different Illuminants . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4682.
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Purpose:To determine how well anomalous trichromats judge surface color under different illuminants and whether their performance is better with surfaces drawn from natural scenes. Methods: Stimuli were simulations of Mondrian–like colored patterns, presented on a computer–controlled monitor. The DeMarco–Pokorny–Smith cone fundamentals for anomalous trichromats (DeMarco et al., 1992, J. Opt. Soc. Am. A, 9, 1465–1476) were used to calibrate a color monitor for deuteranomalous and protanomalous observers, and the Smith–Pokorny cone fundamentals (Smith and Pokorny, 1975, Vision Res., 15, 161–171) were used for normal trichromatic observers. The patterns consisted of 49 abutting 1.0–deg–square uniform surfaces with spectral reflectances drawn at random from natural scenes or, as a control, from the Munsell set. The illuminants were drawn from the daylight locus. In each trial, two images of a pattern were presented in sequence, each for 1 s, with no interval: in the first image, the correlated color temperature of the illuminant was 25000 K or 4000 K, in the second, it was 6700 K. The spectral reflectance of the central square in the second image changed randomly from trial to trial. Observers reported whether there was an illuminant change or a surface–reflectance change. Nine deuteranomalous, five protanomalous, and nine normal trichromatic observers participated in the study. Results:The overall discrimination ability of anomalous trichromats was no different from that of normal trichromats with the two illuminant changes tested here (p = 0.3–0.5; bootstrap tests throughout, paired samples). The discrimination ability of normal trichromats was the same with Munsell and natural spectra regardless of illuminant change (p = 0.2–0.4). The discrimination ability of anomalous trichromats, however, was better with natural spectra than with Munsell spectra for the 4000 K to 6700 K illuminant change, but not for the 25000 K to 6700 K illuminant change. The improvement was significant for the deuteranomalous observers (p = 0.002), but not for the protanomalous observers (p = 0.1). Conclusions: Anomalous trichromats can judge surface color under different daylights as well as normal trichromats, providing that the surfaces are drawn from natural scenes.
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