Unexpected colored shadows: beyond simple additive color mixtures.

The aim of this work was to clarify the difference between two color phenomena: the shadow color, which adds color to the shadows, and the colored shadows, which appears due to the context effect on the color perception. A laboratory photograph is introduced to illustrate the colored shadow effect and how this perceptual effect cannot be explained using classical colorimetry. A yellow colored shadow is observed when two separate white and blue lights illuminate a blank screen and an obstacle occludes part of the light impinging on the screen, and the Retinex Theory is used to explain that phenomenon. [ABSTRACT FROM AUTHOR]