Abstract
Specular highlights on an object under stationary lights move when an observer and/or the object moves. The valid retinal-image motion of highlights enhances percept of gloss (Hartung & Kersten, VSS 2002), and it is further improved when the image motion is induced by observer's voluntary head motion (Araki, et al., APCV 2011; Tani et al., under review). Active manual control facilitates some aspects of visual cognition (eg, object recognition: Harman, et al., Current Biology 1999, temporal vision: Ichikawa & Masakura, Vision Research 2006). We aimed to test whether the retinal-image motion induced by active manipulation of the object further improves glossiness perception. One of five bumpy spheres (15deg diameter) with different specular reflectance (30-50%) was presented for 4s a trial. The average luminance of all spheres was equalized by adjusting diffuse reflectance. The sphere was either stationary or rotated back and forth for 60deg at 0.25Hz on a CRT display (retinal-image motion). Nine participants observed it while they held a ball either with or without manual motion, which was monitored by a motion tracker at 85Hz. In the condition with the retinal-image motion and manual motion, sphere's retinal-image motion was accurately synchronized with participant's hand motion (manual control). Participants were asked to rate sphere's glossiness using visual-analog scale. They performed 16 repetitions of combinations of 2 retinal-image-motion conditions, 2 manual-motion conditions and 5 specular-reflectance conditions in random orders. We found that the perceived glossiness was significantly higher and response variance was smaller with retinal-image motions than without them. However, manual control did not further improve the perceived glossiness. A subsequent experiment (n=8) using low specular reflectance (5-31%) also did not show additional effects of manual control. These results suggest that the valid retinal-image motion of highlights enhances the perceived glossiness and its reliability regardless of whether it is caused by voluntary action.
Meeting abstract presented at VSS 2013