The Role of Lightness Perception in Determining the Perceived Contrast of Real World Scenes

Abstract

We investigate the impact of the background luminance upon the perceived image quality of real world scenes. To do so, we generate a set of small image patches that span the full range of mean luminance values and contrasts that may be displayed upon a monitor with a finite luminance range. Subjects viewed the images on a uniform black, grey or white surround and were asked to rate the perceived quality on a scale from 0 to 9. We find that that the maximum image quality scores occur for images with a mean luminance of less than half, consistent with the image being passed through a compressive non-linearity before contrast is computed. Moreover, the maximum image quality scores occur at lower mean luminance levels when the background luminance is darker, a pattern consistent with investigations into lightness perception. We conclude that models of contrast perception require an adaptive model of lightness perception. However, we also note the considerable challenge of developing a model of lightness perception that can generalize to any given display configuration.

The influence of lightness, and the crispening effect on the perceived contrast of textured images

“…This work directly extends the simple contrast model of [9] by using the empirically estimated lightness functions obtained in experiment one. Thus perceived lightness L is some unknown function of onscreen luminance I:…”

“…The paper is an extension upon [9], which revealed that judgments of image quality are highly correlated with a simple model of contrast perception, detailed in the next section. The study examined quality judgments for small real world images presented on a uniform black, gray or white background.…”

“…It is also found that the surround luminance affects the perceived contrast of a stimulus [1]. Indeed most models of contrast perception pass the stimulus through a luminance nonlinearity prior to computing the image contrast and it has been demonstrated that an adaptive model of the luminance nonlinearity is required before accurate, surround independent estimates of contrast can be made [9].…”