Harold Hill, Vicki Bruce
Effects of Lighting on the Perception of Facial Surfaces
Abstract:A series of experiments is reported which investigated the effects of variations in lighting and viewpoint on the recognition and matching of facial surfaces. Strong effects of lighting were found which interacted with effects of viewpoint. In matching tasks, changing lighting reduced performance, as did changing view, but changing both did not further reduce performance, suggesting that viewpoint and lighting changes affected a common representational process. There were also differences between top and bottom lighting. Recognizing familiar surfaces, and matching across changes in viewpoint were more accurate when lighting was from above than when it was from below the heads, and matching between different directions of top lighting was more accurate than between different directions of bottom lighting. Control experiments demonstrated that the pattern of effects was not dependent upon the artificial materials and task demands used, and that top-lighting also benefited matching between views of unfamiliar objects (amoebae). It is argued that edge- or image-based levels of representation
are not sufficient to explain the results, particularly the observed differences between top and bottom lighting, but that the results do appear consistent with the use of a light-from-above assumption in the interpretation of facial images.