Estimation of Brightness and Lightness in All Adaptation Levels

Brightness and lightness of achromatic suriace 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 llluminance 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.