Colour Constancy as Measured by Least Dissimilar Matching

Abstract

Although asymmetric colour matching has been widely used in experiments on colour constancy, an exact colour match between objects lit by different chromatic lights is impossible to achieve. We used a modification of this technique, instructing our observers to establish the least dissimilar pair of differently illuminated coloured papers. 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. Four trichromatic observers participated in the experiment. The proportion of exact matches was evaluated. When both sets of papers were lit by the same light, the exact match rate 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 exact match rate was 0.80, 0.40, 0.56 and 0.32 for the yellow, blue, green and red lights, respectively. When both lights were chromatic, the exact match rate was found to be even poorer (0.30 on average). Yet, least dissimilar matching was found to be rather systematic. Particularly, a statistical test showed it was symmetric and transitive. The exact match rate was found to be different for different papers, varying from 0.99 (black paper) to 0.12 (purple paper). Such a variation can hardly be expected if observers' judgements were based on an illuminant estimate. We argue that colour constancy cannot be achieved for all the reflecting objects because of mismatching of metamers. We conjecture that the visual system might have evolved to have colour constant perception for some ecologically valid objects at a cost of colour inconstancy for other types of objects.

Object-color-signal prediction using wraparound Gaussian metamers

“…The illuminants are Logvinenko and Tokunaga's [20] red (R2) and neutral (N) as shown in Fig. 6 As another test of the proposed GM prediction method versus von Kries and Bradford, we used the 20 Munsell papers used in the asymmetric matching experiments of Logvinenko and Tokunaga [20] under their green and neutral ("white") illuminants. The spectra of both these illuminants are plotted in Fig.…”

“…As a final test of GM prediction in comparison to von Kries and Bradford prediction, we used all 30 nonidentical pairs of the six Logvinenko and Tokunaga's [20] illuminants shown in Fig. 6.…”

“…9 provide one example. Under the second illuminant this reflectance has XYZ 123; 53; 0.1, whereas the GM method [20]. The plotted colors identify the associated spectrum along with gray indicating N. Solid red indicates R1, and dashed red indicates R2.…”

Study on metamerism degree evaluation based on wavelength sensitive cone weighting algorithm

“…Given the reference illuminant D65, CIE1964 standard colorimetric observer (10 ), and SOCS data set, taking the first color sample in ColorChecker24 color data set as an example, we computed corresponding 53 486 metameric pairs as our metamerism data set M. There are 28 948 metamerism spectral reflectance curves, where the magnitude of each band that do not fall within the range of [0,1] will be deleted. The rest of color samples are deduced by the same, and a total of 24 metamerism data sets are derived.…”

“…Following the recent discovery of color constancy and metamerism mismatching phenomenon, Logvinenko et al argued that color constancy cannot be achieved for all reflecting objects. 10 Moreover, Berns et al suggested that the color differences calculated at constant chromatic adaptation by their proposed method will give greater utility than indices calculated by the normal approach. 11 Wang et al believed that the effect of L* on reflectance is much greater than the effect of saturation (a* or b*).…”