Absolute reflectances from reflectometer readings.

Equations have been derived that allow differences in reflectometer readings of the same sample with various reflectometers to be minimized by placing all reflectances on an absolute basis. For pigmented vehicle films the Fresnel reflectances and transmittances at the air-vehicle interface can be calculated for an arbitrary incident angular light distribution. The form of the reflected and transmitted angular distributions can also be calculated. The equations have been used to determine absolute reflectances of titanium dioxide pigmented films from meter readings of two reflectometers-the General Electric Recording and the Colormaster.