Abstract

When a gray object and a colored object are equated in their lightness as defined by, for example, L* in the CIE l976L*u*v* system, and observed side by side, the colored object looks always brighter than that of gray. A need arises for a new concept, equivalent lightness for these objects so that when both objects are equated in the equivalent lightness, they look equally bright. Equivalent lightness of an object may be defined as the lightness of a gray scale that matches with the colored object in brightness. We have experimentally determined the equivalent lightness of various colored charts at various illuminance levels including scotopic, mesopic and photopic levels to understand the underlying mechanism for brightness perception of colored objects.

© 1992 Optical Society of America