Ding Xiaomao, Radonjic Ana, Cottaris Nicolas P, Jiang Haomiao, Wandell Brian A, Brainard David H
Neuroscience Graduate Group, University of Pennsylvania, Philadelphia, PA, USA.
Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA.
J Vis. 2019 Jul 1;19(7):11. doi: 10.1167/19.7.11.
The spectral properties of the ambient illumination provide useful information about time of day and weather. We study the perceptual representation of illumination by analyzing measurements of how well people discriminate between illuminations across scene configurations. More specifically, we compare human performance to a computational-observer analysis that evaluates the information available in the isomerizations of cone photopigment in a model human photoreceptor mosaic. The performance of such an observer is limited by the Poisson variability of the number of isomerizations in each cone. The overall level of Poisson-limited computational-observer sensitivity exceeded that of human observers. This was modeled by increasing the amount of noise in the number of isomerizations of each cone. The additional noise brought the overall level of performance of the computational observer into the same range as that of human observers, allowing us to compare the pattern of sensitivity across stimulus manipulations. Key patterns of human performance were not accounted for by the computational observer. In particular, neither the elevation of illumination-discrimination thresholds for illuminant changes in a blue color direction (when thresholds are expressed in CIELUV ΔE units), nor the effects of varying the ensemble of surfaces in the scenes being viewed, could be accounted for by variation in the information available in the cone isomerizations.
环境光照的光谱特性提供了有关一天中的时间和天气的有用信息。我们通过分析人们在不同场景配置下区分光照的能力的测量结果，来研究光照的感知表征。更具体地说，我们将人类的表现与一种计算观察者分析进行比较，该分析评估了模型人类光感受器镶嵌体中视锥光色素异构化中可用的信息。这种观察者的表现受到每个视锥中异构化数量的泊松变异性的限制。泊松限制的计算观察者的总体敏感度水平超过了人类观察者。这是通过增加每个视锥异构化数量中的噪声量来建模的。额外的噪声使计算观察者的总体表现水平与人类观察者的表现水平处于同一范围内，从而使我们能够比较不同刺激操作下的敏感度模式。计算观察者无法解释人类表现的关键模式。特别是，无论是蓝色方向上光源变化的光照辨别阈值的升高（当阈值以CIELUV ΔE单位表示时），还是所观察场景中表面集合变化的影响，都无法通过视锥异构化中可用信息的变化来解释。
