Effect of Directional and Diffused Lights on the KANSEI Evaluation of a Glossy Object and the Scene

Abstract

Advances of lighting technology make it possible to realize various types of space lighting from strongly directional to highly uniform. In this study, the effect of mixture ratio of directional and diffused light on KANSEI evaluations of the object and scene, black lacquer bowl with tofu sample in nearly uniform and achromatic background is investigated. Subjective evaluations were carried out under various lighting conditions using 15 adjective pairs, such as “ Non-glossy vs Glossy ” , “ Soft vs Hard ” , and “ Ugly vs Beautiful ” , etc., that were selected in the pre-experiment. Results of the subjective evaluation for the adjective pairs are divided into 3 groups in relation to lighting quality. Group 1 that reflect surface property of the object such as “ Non-glossy vs Glossy ” , correlate primarily to highlight luminance with mild correlation to the luminance of non-highlight area, whereas those of Group 2 that reflect nonvisual physical properties such as “ Soft vs Hard ” , correlate primarily to the luminance of non-highlight area with almost no effect from directional light. Adjective pairs of Group 3 that reflect to higher order values of object and/or scene such as “ Cheap vs Luxury ” or “ Realistic vs Fantastic ” , correlate strongly to the luminance contrast between highlight and non-highlight areas.