Abstract
In the preceding paper, we investigated how noise affects sharpness perception, using white noise and one- and two-dimensional uni-frequency patterns as stimuli. The result showed sharpness of higher frequency stimuli decreased with increased noise, while that of lower frequency stimuli increased at certain levels. From this result, we thought noise reduces sharpness at edges, but can sharpen lower frequency component or texture of the image. In this study low frequency noise or white noise were applied to natural pictures. They were two pictures of tree bark. There was no large difference in their power spectrum, but one had clear edges, and the other did not. The results showed that addition of noise to the picture possessing edges decreased sharpness especially in the case of white noise, whereas noise addition to the picture possessing no edges resulted in sharpness increase at a certain noise level. This suggests that sharpness improvement effect by noise addition depends on whether edges exist or not.
