Logvinenko Alexander D, Tokunaga Rumi
Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow G4 0BA, UK.
Seeing Perceiving. 2011;24(5):407-52. doi: 10.1163/187847511X588746. Epub 2011 Sep 6.
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.
尽管非对称颜色匹配已广泛应用于颜色恒常性实验中，但要在由不同色光照明的物体之间实现精确的颜色匹配是不可能的。我们对该技术进行了改进，指示观察者找出照明不同的彩色纸张中差异最小的一对。刺激显示由两组相同的22张孟塞尔纸张组成，分别由中性光、黄光、蓝光、绿光和红光独立照明。这些光产生的照度大致相同。四名三色视觉观察者参与了实验。评估了精确匹配的比例。当两组纸张由相同的光照明时，中性光、黄光、蓝光、绿光和红光的精确匹配率分别为0.92、0.93、0.84、0.78和0.76。当一种照明是中性的而另一种是彩色的时，黄光、蓝光、绿光和红光的精确匹配率分别为0.80、0.40、0.56和0.32。当两种光都是彩色的时，发现精确匹配率甚至更低（平均为0.30）。然而，发现差异最小的匹配相当有系统性。特别是，一项统计测试表明它是对称的和可传递的。发现不同纸张的精确匹配率不同，从0.99（黑色纸张）到0.12（紫色纸张）不等。如果观察者的判断是基于对照明的估计，很难预期会有这样的变化。我们认为，由于同色异谱现象的不匹配，并非所有反射物体都能实现颜色恒常性。我们推测，视觉系统可能已经进化到对某些具有生态有效性的物体具有颜色恒常感知，而以牺牲其他类型物体的颜色恒常性为代价。
