Abstract
Our visual system can perceive glossiness not only from high-luminance regions (e.g., specular highlights) but also from low-luminance regions of object images (Fleming et al., 2003; Kim et al., 2012). The authors recently reported that high spatial frequency components, such as luminance edges, on a glossy object surface well correlated to magnitude of perceived glossiness not depending on specular highlights (Kiyokawa et al., 2019). Here, we examined whether emphasizing the contrast of high spatial frequency components increases perceived glossiness in two psychophysical experiments. In the first experiment, we quantified dependency of perceived glossiness on specular highlight. The stimuli were 108 glossy object images with and without specular highlights (referred to as Full and Dark condition, respectively) generated by a computer graphics software, Mitsuba. The observers rated perceptual glossiness on these stimuli. On the basis of the rating results, the stimuli were divided into two groups: the high highlight-dependency (HHD) group, in which scores were significantly larger in Full condition than in Dark condition, and the low highlight-dependency (LHD) group, in which scores were comparable between the highlight conditions. In the second experiment, high spatial frequency contrast in the stimulus images were enhanced with a Laplacian-based filter with different strengths. Two images with different enhancement strengths were simultaneously presented side-by-side, and the observers judged which image seemed glossier in the 2AFC manner. The results showed that perceived glossiness increased with strengths of high-frequency contrast enhancement in both highlight conditions. However, in Dark condition, the glossiness enhancement effect of the filtering was significantly stronger in the LHD group than in the HHD group. These results suggest that enhancement of high-frequency contrast is effective for manipulating the strength of perceived glossiness and, in particular, the effects are more prominent for object images on which glossiness perception does not depend on specular highlights.