Brown L G, Rudd M E
Lions Low Vision Center, Johns Hopkins Wilmer Eye Institute, Baltimore, MD 21205, USA.
Vision Res. 1998 Jun;38(13):1925-33. doi: 10.1016/s0042-6989(97)00400-8.
For small, brief targets incremental threshold is known to obey the de Vries-Rose law: threshold rises in direct proportion to the square-root of background intensity. We present data demonstrating a square-root law for brightness matching as well. The square-root law for brightness is obtained over the full range of scotopic vision, and the low intensity end of photopic vision. The classic theory of de Vries and Rose explains the square-root law on the basis of increased variability of the photon count as the background increases. Our brightness matching data instead indicates that the mean signal level is reduced by a factor which is inversely proportional to the standard deviation of the photon count. This result is consistent with the idea that in the retina there exists a gain control mechanism that is sensitive to the variance in the photon input, rather than to the mean illuminance. The importance of this idea to the modelling of retinal gain controls is discussed.
对于小的、短暂的目标，已知增量阈值遵循德弗里斯 - 罗斯定律：阈值与背景强度的平方根成正比增加。我们展示的数据表明亮度匹配也遵循平方根定律。亮度的平方根定律在暗视觉的整个范围内以及明视觉的低强度端都能得到。德弗里斯和罗斯的经典理论基于随着背景增加光子计数变异性增加来解释平方根定律。相反，我们的亮度匹配数据表明平均信号水平降低的系数与光子计数的标准差成反比。这一结果与视网膜中存在对光子输入方差敏感而非对平均照度敏感的增益控制机制这一观点一致。讨论了这一观点对视网膜增益控制建模的重要性。
