Understanding Lightness and Brightness in Different Media

This thesis aimed to study how lightness and brightness perception relate to each other. We used a simple task to study whether observers perceive lightness and brightness to be different percepts and what cues they use to make these judgments. In Experiment 1, we used a custom-built apparatus to present two reflectance patches, each with independent illuminance. In the lightness and brightness conditions, observers judged which patch had a higher reflectance or luminance, respectively. In Experiment 2, we repeated the same procedure using a computer rendering of the apparatus on a monitor. Finally, we simulated computational models of lightness and brightness to evaluate their performance with respect to observer performance. We conclude that (a) lightness and brightness judgments are more similar than expected from previous work, (b) brightness is nothing like an estimate of luminance, and (c) current computational models can fail on even simple lightness and brightness judgments.