Effect of illuminating and viewing geometry on the color coordinates of samples with various surface textures

Color measurements with several different illuminating/viewing geometries were carried out for samples with four different surface textures in four different colors: matte papers, glossy papers, ceramic or porcelain enamel tiles, and polished opaque glasses, with ISCC-NBS color designations moderate pink, pale orange-yellow, dark bluish-green, and dark gray. On a single instrument (Cary 14 spectrophotometer), three geometries were used: normal/diffuse (N/D), diffuse/normal (D/N) and normal/45 degrees (N/45). For comparison, measurements were also made on a GE spectrophotometer (GERS) using near-normal/diffuse geometry. All integrating sphere (diffuse) measurements were made with specular component both included and excluded. Specular gloss and goniophotometric reflectance measurements were made. For these samples, the Cary 14 N/D and GERS results are in good agreement, and the results with N/D and D/N geometries are essentially equivalent, but there is strong evidence of the serious problem of incomplete exclusion of the specular component with all of the integrating sphere geometries when operated in the specular-excluded mode, even with samples normally considered to be highly glossy or highly matte.