Roughness vs. contrast in natural textures

We investigate the effect of contrast enhancement on the subjective roughness of visual textures. Our analysis is based on subjective experiments with seventeen images from the CUReT database in three variants: original, synthesized textures, and contrast-enhanced synthesized textures. In Experiment 1, participants were asked to adjust the contrast of a synthesized image so that it became similar in roughness to the original image. A new adaptive procedure that extends the staircase paradigm was used for efficient placement of the stimuli. In Experiment 2, the subjective roughness and the subjective contrast of the original, synthesized, and contrastenhanced synthesized images were determined using a pairwise comparison paradigm. The results of the two experiments show that although contrast enhancement of a synthesized image results in a similar subjective roughness as the original, the subjective contrast of that image is considerably higher than that of the original image. Future research should give more insights in the interaction between roughness and contrast.