A method of measurement of geometric metamerism on the metallic paint films was studied and their results were considered. In the case of gonio-colorimetry, correction of illumination should be taken according to geometric specification of a photometer. Using the suitable correction, the solid color paint film showed the same color stimuli at an arbitrary angle of incidence and viewing. In contrast with this, the metallic paint shows geometric metamerism. When the angles between specular reflection and viewing are equal, the color stimuli are the same. The optical properties of color pigments such as coefficients of scattering and absorption influence on geometric metamerism. Two kinds of phthalocyanine blue the authors used have almost the same mass color. However, they showed considerable different behavior on geometric metamerism.
In order to make the easy and precise conversion between chromaticity coordinates and dominant wavelength, excitation purity, an algorithm for using micro-computer has been studied. A BASIC-program, based on this algorithm, could offer saving time and tedium, also sufficient accuracy and precision of the computed results in comparison with the graphical determination.