Dr. Yoko Mizokami is an Associate Professor in the Division of Information Science, Graduate School of Advanced Integration Science, Chiba University, Japan.
She received a Ph.D. in Engineering in 2002 from Ritsumeikan University, Japan. From 2002-2006 she was a postdoctoral fellow at the University of Nevada, Reno, Department of Psychology. She moved to Chiba University in 2006.
Her research interests lie in color vision, color science, and vision in natural environments. The current research topics cover the influence of lighting to object appearance, the appearance of skin color and texture, the perception of image color difference, colorfulness adaptation, and vision deficiency.
She received the Konica Minolta Imaging Science Encouragement Award, 2015, the Indow Taro Award, 2010, the Illuminating Engineering Institute of Japan, 2000 and the Optical Society of Japan Award, 1999. She is a member of International Colour Vision Society (ICVS), Vision Sciences Society, OSA, Vision Society of Japan, Color Science Association of Japan, Optical Society of Japan, and the Illuminating Engineering Institute of Japan.

Abstract: Influence of Diffusibility of Illumination on the Appearance of Colour and Surface Properties

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.