väriconstanssi

Väri-konstanssi, or color constancy, is a perceptual phenomenon in which the perceived color of a surface remains relatively stable under varying illumination. People can recognize objects and their colors even as light sources change from daylight to artificial lighting, although the effect is not perfect and can be influenced by context and scene lighting.

The phenomenon arises from multiple interacting processes in the visual system. Chromatic adaptation adjusts the sensitivity of color detectors in the eye to the prevailing illumination. Contextual and spatial cues, such as surrounding colors and shading, help the brain infer the true surface color. Higher-level interpretation and memory also contribute, allowing stable color judgments across different environments.

Theoretical approaches to color constancy include early models based on chromatic adaptation, such as von Kries-type transforms, and more comprehensive theories like Band and Retinex perspectives. Edwin H. Land’s Retinex theory emphasizes cortical processing that compares color signals across the visual field to achieve consistent color appearance. Modern color appearance models, such as CIECAM02, integrate chromatic adaptation with illumination and viewing conditions to predict perceived colors.

Applications of color constancy research span photography, film, and digital imaging, where white balance and color management seek to reproduce colors faithfully under diverse lighting. In computer vision, algorithms attempt to estimate illumination to achieve consistent color recognition in varying scenes. Color constancy remains an area of active study, balancing low-level sensory mechanisms with high-level interpretation.