Worthey J A
J Opt Soc Am. 1982 Jan;72(1):74-82. doi: 10.1364/josa.72.000074.
Starting with an opponent-colors formulation of color vision, two parameters, t and d, may be defined that express an illuminant's ability to realize red-green and blue-yellow contrasts of objects. For instance, calculation of t and d for daylight shows that on a gray day, color contrasts are actually reduced. By these measures, many common vapor-discharge illuminants systematically distort object colors. Because red-green contrasts contribute to border distinctness, and both types of color contrast contribute to brightness, such systematic distortions probably affect the overall clarity and brightness of what is perceived visually, Experimental data are consistent with this idea. In relation to color-constancy (retinex) experiments, it is approximately true that the visual system discounts the color of an illuminant but not its t and d.
从色觉的对立色公式出发，可以定义两个参数t和d，它们表示光源实现物体红-绿和蓝-黄对比度的能力。例如，对日光的t和d计算表明，在阴天时，颜色对比度实际上会降低。通过这些测量方法，许多常见的气体放电光源会系统性地扭曲物体颜色。由于红-绿对比度有助于边界清晰度，且两种颜色对比度都对亮度有影响，这种系统性扭曲可能会影响视觉感知的整体清晰度和亮度。实验数据与这一观点一致。就颜色恒常性（视网膜皮层理论）实验而言，视觉系统大致上会忽略光源的颜色，但不会忽略其t和d值，这一说法大致是正确的。
