contrastam

Contrastam is a fictional term used to describe a contextual, adaptation-aware measure of visual contrast in discussions of perceptual science and image processing. In this article, contrastam is defined as the perceptual difference between two image regions, taking into account not only their luminance difference but also the local adaptation state, surrounding luminance, chromatic context, and temporal changes. It is not an officially standardized metric and is treated here as a conceptual tool for exploring how humans perceive contrast in realistic viewing conditions.

Conceptually, contrastam extends the idea that contrast sensitivity depends on more than absolute luminance. A proposed model would describe contrastam as a function of luminance difference, local mean luminance, adaptation level, surround contrast, color context, and timing. Under higher adaptation to a bright field, for example, the same luminance difference might yield a smaller perceptual contrast, whereas in a dark surround, the same difference could appear more pronounced. This context-sensitivity aligns with known psychophysical principles such as contrast adaptation and Weber-like behavior, but contrasts with more simplistic, context-agnostic measures of contrast.

Applications of the fictional concept include informing tone-mapping algorithms for high-dynamic-range images, guiding edge-detection and contrast-enhancement methods, and providing a framework for discussing perceptual quality in display design. Critics note that, as a nonstandard concept, contrastam lacks precise definitions and experimental consensus. See also contrast sensitivity, tone mapping, Weber’s law.