Effect of image characteristics of edge-grain patterns on visual impressions

To demonstrate the psychophysical effect of edge-grain patterns on visual impressions received by human observers, printed images of the edge-grain patterns of 16 species were prepared as well-regulated visual stimuli, and impressions of the patterns on 32 subjects were evaluated using six categories. Image characteristics of the patterns were expressed numerically using contrast values that were derived by multi-resolution contrast analysis (MRCA) proposed by the authors, and relationships between the image characteristics and the visual impressions were examined. The difference in lightness between local areas with a certain size in the image was used as the contrast value, which could be used to detect the change in lightness due to the particular feature in the edge-grain pattern. While some impressions were almost independent of the contrast values, other impressions showed highly positive or negative linear relationships to the contrast values, derived at the optimal filter size in MRCA. Moreover, these optimal sizes were rarely affected by color information. The contrast value proposed in this paper would be a good numerical index that could be used not only to describe image characteristics of the edge-grain patterns but also to estimate some of their visual impressions.