Abstract
The objects in our environment are made from a wide range of materials. The color appearance of the objects is influenced by the geometry of the illumination, the three-dimensional structure of the objects, and the surface reflectance properties of their materials. Only few studies have investigated the effect of material properties on color perception. In most of these studies the stimuli were three-dimensional objects rendered on a computer screen. Here we set out to investigate color perception for real objects made from different materials. The surface properties of the materials ranged from smooth and glossy (porcelain) to matte and corrugated (crumpled paper). We tested objects with similar colors made from different materials and objects made from the same material that differed only in color. The objects were placed on black cloth in a chamber under controlled lighting conditions. In an asymmetric matching task observers matched the color and lightness of the objects by adjusting the chromaticity and the luminance of a homogeneous, uniformly colored disk presented against a black background on a CRT screen. The screen was located close to the objects so that it was not directly illuminated by the lamps that illuminated the objects. To determine the chromatic and luminance distributions of the objects their surfaces were measured with a spectroradiometer at numerous points from the viewpoint of the observers. We also measured the chromatic and luminance distributions of the materials when they could be presented as approximately flat surfaces (paper and wool). The observers' matches were measured with the spectroradiometer. In general observers' matches were close to the true chromatic and luminance distributions due to the objects. However, observers systematically tended to discount the variations in reflected light induced by the geometry of the objects and rather matched the light reflected from the materials themselves.
Supported by DFG grant Ge 879/9.