An Estimation of Lightness with Visual Agreement

Abstract

Spectrophotometers to measure object-colors are generally divided into two types of measuring geometry as 45-degree, 0/45, and integrating sphere, d/8, and the latter is furthermore classified into two modes, namely, specular component include (SCI) and specular component exclude (SCE). However, according to the difference of these types of measuring geometry, each colorimetry result with the same sample can be considerably different from others, because of the influence of the component reflected normally from the sample surface. This will cause extremely confusing matters, in particular, if a dark sample is glossy. In this article, we have examined the differences of metric-lightness with these geometric conditions, and come to the conclusion that any measured result for glossy samples should be related to a correlation of gloss in order to match human perception under a common viewing condition, that is an illuminated environment of a general office. And furthermore, we have proposed an estimation model that gives a visual lightness for object-colors, which is independent of different kinds of measuring geometry.