Color appearance of real objects varying in material, hue, and shape

The objects in our environment are made of a wide range of materials. The color appearance of the objects is influenced by many factors, including the geometry of the illumination, the shape of the objects, and the reflectance properties of their materials. Only few studies have investigated the effect of material properties on color perception, mostly with stimuli rendered on a computer screen. Here we set out to investigate color perception for real objects made of different materials. The surface properties of the materials ranged from smooth and glossy to matte and corrugated. We tested objects with similar colors made from different materials and objects made from the same material that differed only in color. Observers matched the color appearance of the objects by adjusting the chromaticity and the luminance of a homogeneous, uniformly colored disk presented on a CRT screen. The observers matched the hue of the objects quite accurately. Chroma matches were modulated by the lightness of the objects. For dark objects, chroma was overestimated, while for light objects it was underestimated. For lightness, observers matched the brightest points of the objects excluding highlights. This is a suitable strategy to compensate for variations in surface geometry and illumination.