Pas Susan F Te, Pont Sylvia C, Dalmaijer Edwin S, Hooge Ignace T C
Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, the
Perceptual Intelligence Lab, Faculty of Industrial Design Engineering, Delft University of Technology, Delft, the
J Vis. 2017 Jul 1;17(8):2. doi: 10.1167/17.8.2.
Human observers are able to successfully infer direction and intensity of light from photographed scenes despite complex interactions between light, shape, and material. We investigate how well they are able to distinguish other low-level aspects of illumination, such as the diffuseness and the number of light sources. We use photographs of a teapot, an orange, and a tennis ball from the ALOI database (Geusebroek, Burghouts, & Smeulders, 2005) to create different illumination conditions, varying either in diffuseness of a single light source or in separation angle between two distinct light sources. Our observers were presented with all three objects; they indicated which object was illuminated differently from the other two. We record discrimination performance, reaction times, and eye fixations. We compare the data to a model that uses differences in image structure in same-object comparisons, and outcomes suggest that participants mostly rely on the information contained in cast shadows and highlights. The pattern of eye fixations confirms this, showing that after the first fixation, observers mostly fixate cast shadow areas. However, information in the highlights is rather salient, so it might be available from first fixation, making separate fixations are unnecessary.
尽管光线、形状和材质之间存在复杂的相互作用，但人类观察者仍能够从拍摄的场景中成功推断出光线的方向和强度。我们研究了他们区分照明其他低层次方面的能力，比如漫射程度和光源数量。我们使用了来自ALOI数据库（Geusebroek、Burghouts和Smeulders，2005年）的茶壶、橙子和网球的照片来创建不同的照明条件，这些条件在单个光源的漫射程度或两个不同光源之间的分离角度方面有所变化。我们向观察者展示了所有三个物体；他们指出哪个物体的照明与其他两个不同。我们记录辨别性能、反应时间和眼睛注视情况。我们将数据与一个在同一物体比较中使用图像结构差异的模型进行比较，结果表明参与者大多依赖投射阴影和高光中包含的信息。眼睛注视模式证实了这一点，表明在第一次注视之后，观察者大多注视投射阴影区域。然而，高光中的信息相当显著，所以可能从第一次注视时就可以获取，无需进行单独的注视。
