The BRDF (Bidirectional Reflectance Distribution Function) gives the reflectance of a target as a function of illumination geometry and viewing geometry. The BRDF depends on wavelength and is determined by the structural and optical properties of the surface, such as shadow-casting, multiple scattering, mutual shadowing, transmission, reflection, absorption and emission by surface elements, facet orientation distribution and facet density.
However, it shouldn’t be overlooked that the BRDF simply describes what we all observe every day: that objects look differently when viewed from different angles and when illuminated from different directions.
Epner’s diffuse Laser Gold coating specified primarily on integrating spheres, has been measured at Schmitt Measurement Systems, Inc. The measurements were made at 10.6 microns on a mechanically diffused surface.