The appearance of object surface could be largely influenced by lighting conditions such as color, direction and diffuseness. The diffuseness of illumination would change the components of specular and diffuse reflection resulting difference in the perceived quality of object surface. However, it has not been systematically analyzed how color and surface appearance of an object is influenced by the diffuseness.
We investigated how the impression of surface appearance of test samples changes under diffused light and direct light using real samples in real miniature rooms. We prepared plane gray test samples with three different levels of surface roughness and gray spheres with matt and gloss surface. A sample was placed in the center of a miniature room with either diffuse or directed light, and observer evaluated its appearance. We used a semantic differential method to examine what types of factors were influenced by the diffusibility of illumination. The result of analysis based on 20 adjective-pairs showed that glossiness and smoothness were main factors. Samples tended to appear less glossy and smother under diffused light than under direct light, and their difference was larger for a sample with rough surface.
We also examined the color appearance of several color samples under diffused light and direct light by selecting corresponding color from a Munsell color chart placed in a separate viewing box. The results of corresponding color were similar in both lighting conditions, suggesting color appearance was stable at least for samples that we tested.
Our results suggest that the appearance of surface qualities such as glossiness and smoothness are more influenced by the diffusibility of illumination than color appearance. It also implies that the surface properties of objects should be considered when examining the influence of diffusibility of illumination on surface appearance.