Golz Jürgen, MacLeod Donald I A
Department of Psychology, University of Kiel, 24098 Kiel, Germany.
Nature. 2002 Feb 7;415(6872):637-40. doi: 10.1038/415637a.
The light reflected from an object depends not only on the surface properties of this object but also on the illuminant. The same is true for the excitations of the photoreceptors, which serve as the basis for the perceived colour. However, our visual system has the ability to perceive constant surface colours despite changes in illumination. The average chromaticity of the retinal image of a scene depends on the illumination, and thus might be used by the visual system to estimate the illumination and to modulate the correction that subserves colour constancy. But this measure is not sufficient: a reddish scene under white light can produce the same mean stimulation as a neutral scene in red light. Higher order scene statistics-for example, the correlation between redness and luminance within the image-allow these cases to be distinguished. Here we report that the human visual system does exploit such a statistic when estimating the illuminant, and gives it a weight that is statistically appropriate for the natural environment.
从物体反射的光不仅取决于该物体的表面特性，还取决于光源。对于作为感知颜色基础的光感受器的激发来说也是如此。然而，尽管光照发生变化，我们的视觉系统仍有能力感知恒定的表面颜色。场景视网膜图像的平均色度取决于光照，因此视觉系统可能会利用它来估计光照，并调节有助于颜色恒常性的校正。但这种测量方法并不充分：白光下的红色场景可能产生与红光下的中性场景相同的平均刺激。更高阶的场景统计数据——例如，图像中红色与亮度之间的相关性——可以区分这些情况。我们在此报告，人类视觉系统在估计光源时确实会利用这样一种统计数据，并赋予它一个在统计上适合自然环境的权重。
