Estimation of Brightness and Lightness in All Adaptation Levels

Abstract

Brightness and lightness of achromatic surface colors were evaluated under various illuminance conditions in order to make a brightness scale that can be applied for all adaptation levels. A pair of gray scales made up of six gray color chips were presented in a test field and a reference field. Brightness as well as subjective lightness of the six test colors were evaluated using a gray scale in the reference field. Not only haploscopic and also binocular viewing conditions were employed. Furthermore, two comparison techniques-a conventional direct comparison method and a newly developed cascade comparison method-Were used in the case of brightness criterion. Experimental results show that the perceived contrast decreased with decreasing illuminance for the brightness criteria.The contrast compression for a cascade comparison was larger than that for a direct comparison. No contrast compression was obtained for the criterion of subjective lightness.