As the exterior paint colors of automobiles change the shade of color and brightness according to viewing angle, the appearance of a paint finish is expressed numerically by the reflection characteristic (i.e. reflectance) of paint surface. We figure out that the reflectance of most automotive paint finishes is best measured at the incident angle of 60 degrees and the five aspecular angles of 10 degrees, 18 degrees, 28 degrees, 40 degrees, and 90 degrees on the incident plane (Color Res Appl 2005;30.-275-282). However, in the case of the so-called color shift paint, which changes its paint finish appearance as a jewel beetle, depending on the light source location, the reflection characteristic can not be expressed accurately by conventional measuring methods. As the directions not included in the incident plane need to be taken into account, we have to measure at 48,139 points, changing all the incident angles and reflected angles. (It would take about 16 days.) We, therefore, tried to reduce the number of combinations of incident and reflected angles by analyzing the experimental data. Consequently, we reduced it to 1485 points (about 4 h). When we numerically compared our result to the result of all measuring points, we found that the color difference is 2.76 and therefore our method is practically usable. (c) 2007 Wiley Periodicals, Inc.