Analysis of Color Fade Phenomenon in Studies on the Multi-Angle Characterization of Spectral Reflectance Standards

This paper describes the new aspects to be taken into account in the calibration procedures for reflectance spectrophotometers used at the Central Office of Measures in Warsaw, Poland. The measurement set-up for the multi-angled characterization of the spectral reflectance standards is presented. The main problem considered in this publication is the insufficient knowledge of the wide angular characteristics of the sample tested in reflected light, what affects accuracy and, consequently, uncertainty in the process of dissemination of the units of measurement during the calibration of reflectance spectrophotometers. The results of tests for a wider range of the angle of reflection are presented here, with particular attention paid to the study of the actual limits of the color characteristics for ceramic chromatic standards. The basic calculation formulas used in reflectance colorimetry are presented and applied to prepare extended reflectance characteristics of standards in the tested angle of incidence and angle of reflection configurations. Based on these analyses, conclusions were presented.