The following is a summary of “Conjoint measurement of perceived transparency and perceived contrast in variegated checkerboards,” published in the February 2022 issue of Ophthalmology by Aguilar, et al.

An important question in vision research was how the visual input received by the retina is segmented into relevant perceptual variables. Transparency perception is an example of the segmentation process, where the luminance information in one location contributes to two perceptual variables: the properties of the transparent medium and the background. Previous studies have suggested that perceived transparency is closely related to perceived contrast, but the relationship between the two and retinal luminance has yet to be established. 

The study used maximum likelihood conjoint measurement (MLCM) to investigate the relationship between perceived transparency, perceived contrast, and image luminance. The stimuli used were images of variegated checkerboards composed of multiple reflectances and partially covered by a transparent overlay, with the transmittance and reflectance of the transparent medium systematically varied. Perceptual scales for perceived transparency and perceived contrast were measured, and they were found to follow a remarkably similar pattern across observers. 

Researchers tested the empirically observed scales against predictions from various contrast metrics and found that perceived transparency and perceived contrast were equally well predicted by a metric based on the logarithm of Michelson or Whittle contrast. 

Thus, the study concluded that judgments of perceived transparency and perceived contrast were likely to be supported by a common mechanism, which can be computationally captured as a logarithmic contrast.

Reference: jov.arvojournals.org/article.aspx?articleid=2778331