Contribution of luminance to the perceptual “Clarity/Cloudiness” in transparency for achromatic stimuli

Tsirlin et al. (2012) refer to perceptual transparency with clarity as glass-transparency, and that with cloudiness as translucency. The present study involving overlapping achromatic figures examined how glass-transparency and translucency are influenced by overlapping and non-overlapping areas on transparent surfaces and the level of luminance of the background. Experiments were conducted with three different backgrounds (white, black, and light gray) and varying levels of luminance in overlapping (Experiment 1) and non-overlapping (Experiment 2) areas. The subjects were asked about the clarity and cloudiness of the stimuli, and chose from response options including “very clear” and “very cloudy”. The results suggested that the larger the difference in the level of luminance between overlapping and non-overlapping areas, and the smaller the difference in luminance between non-overlapping area and the background, the less the “cloudiness”, or the greater the “clarity”. The results were uniformly explained according to the ratio of differences in the level of luminance between two areas and the level of luminance of the background.