Introduction: Human observers seem to robustly and effortlessly classify material properties, even when the optical input changes completely due to illumination changes. Previous research by Fleming et al. (2003) shows that the complexity of the illumination affects our judgments of glossiness. Here, we investigate the effects of both the nature of the illumination and the presence of context objects on the perceived glossiness of a reference object. Method: We compare perceived glossiness for complicated illumination (containing high frequency variations in the spatial luminance distribution, a bit like sunlight filtered through foliage), collimated illumination and diffuse illumination. As context objects, we use an arrangement of fruits, vegetables and vases that all either retained their original color and glossiness, were all spray painted matte gray, or were all spray painted specular gray. Participants viewed a gray reference object in that was either photographed in isolation or placed in a number of complex scenes, under three different illuminations. They matched the glossiness of a test object that was photographed in isolation on a matte background with collimated illumination to the glossiness of this reference object. Results: We found a huge underestimation of the glossiness of the object when the object was illuminated with a diffuse light source, compared to when the object was illuminated with a collimated light source, whereas glossiness was overestimated when illuminated with a highly complicated light source. In some participants, these biases were slightly reduced when specular or colored context objects were present. Conclusions: Results indicate that a richer environment, with complicated, more natural, illumination and a variety of different context materials, help us judge glossiness more accurately.
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