Luminous Reflectance

Luminous Reflectance, transmittance and color. This test is the primary method to obtain colorimetric data. Properties determined include: 1 ) total luminous reflectance or luminous directional reflectance; 2) luminous transmittance; and 3 ) chromaticity coordinates x and y (color).

A specimen is mounted in a special device and along with it a comparison surface (white chalk). The specimens are placed in the device and light of different wave-length intervals is impinged against the surface. Reflected or transmitted light is then measured to obtain property values. ASTM D-791.