Method for estimating reflectance

Abstract

A reflectance of a color shifted painting color is also measured conveniently. A first reflectance R(α) of a first reflected light Vinside an incident plane A is measured, and a first locus l of termini of first bisection vectors H(|H|=|R(α)|), which displaces two-dimensionally inside the incident plane A, is determined. A second reflectance R(α) of a second reflected light Voutside the incident plane A is measured, and a second locus m of termini of second bisection vectors H(|H|=|R(α)|), which displaces three-dimensionally outside the incident plane A, is measured. A locus n (x, y, z) of a terminus of a bisection vector Hon a plane z=z that is parallel to a plane under measurement is approximately modeled with a numerical equation showing an ellipse from the first locus l and the second locus m, thereby determining an approximation model equation, and an overall locus n' (x, y, z) of the overall termini of bisection vectors H′ of reflected lights V′ other than the first reflected light Vand the second reflected light Vis approximately determined.