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Alexander D. Logvinenko, Rumi Tokunaga; Colour constancy as measured by least dissimilar matching. Journal of Vision 2010;10(7):396. doi: 10.1167/10.7.396.
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Colour constancy is usually measured with the asymmetric colour matching technique. As an exact colour match between objects lit by different chromatic lights is impossible, we instructed our observers to establish the least dissimilar pair when studying colour constancy. Using such a technique, Logvinenko & Maloney (2006) found nearly perfect lightness constancy. The stimulus display consisted of two identical sets of 22 Munsell papers illuminated independently by neutral, yellow, blue, green and red lights. The lights produced approximately the same illuminance (50 lux). Their CIE 1931 chromaticity coordinates were (0.303, 0.351), (0.392, 0.410), (0.131, 0.150), (0.224, 0.667), and (0.635, 0.321). Four trichromatic observers participated in the experiment. Pointing out randomly a paper under one illumination, experimenter asked observer to indicate which paper under the other illumination appeared least dissimilar in colour. All measurements were repeated three times for each observer. When the least dissimilar match was the physically same paper we call it exact match. The proportion of exact matches was evaluated as a colour constancy index (CCI). When both the sets of papers were lit by the same light, the CCI was 0.92, 0.93, 0.84, 0.78, and 0.76 for the neutral, yellow, blue, green and red lights respectively. When one illumination was neutral and the other chromatic, the CCI was 0.80, 0.40, 0.56, and 0.32 for the yellow, blue, green and red lights respectively. Therefore, the simultaneous colour constancy was found to be much poorer. Yet, it was better than expected if one takes into account the illuminant induced colour stimulus shift as defined by Logvinenko (2009). Therefore, the visual system somehow overcomes the limitations on colour constancy imposed by the illuminant induced colour stimulus shift. References Logvinenko A. D. & Maloney L. T. (2006) Perception & Psychophysics, 68, 76-83. Logvinenko A. D. (2009) J. of Vision 9(11):5.
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