The perception and misperception of specular surface reflectance

The amount and spectral content of the light reflected by most natural surfaces depends on the structure of the light field, the observer's viewing position, and 3D surface geometry, particularly for specular (glossy) surfaces. A growing body of data has demonstrated that perceived surface gloss can vary as a function of its 3D shape and its illumination field, but there is currently no explanation for these effects. Here, we show that the perception of gloss can be understood as a direct consequence of image properties that covary with surface geometry and the illumination field. We show that different illumination fields can generate qualitatively different patterns of interaction between perceived gloss and 3D surface geometry. Despite the complexity and variability of these interactions, we demonstrate that the perception (and misperception) of gloss is well predicted by the way that each illumination field modulates the size, contrast, sharpness, and depth of specular reflections. Our results provide a coherent explanation of the effects of extrinsic scene variables on perceived gloss, and our methods suggest a general technique for assessing the role of specific image properties in modulating our visual experience of material properties.