Measurement of Luminance Factor

Abstract Luminance factor of a diffusing material is defined as the ratio of the luminance of the surface of the material to that of a perfect (Lambertian) diffuser under specified conditions of illuminance and angle of view. Measurement of this quantity has always been rather difficult, involving visual photometric measurements at widely different levels of illuminance. A physical method of measuring luminance factor is described which has given more repeatable results and better interlaboratory agreement than the former visual method.