\(R = \frac{\Phi_n}{\Phi_d}\), where \(\Phi_n\) is the radiant flux or luminous flux reflected in the directions delimited by a given cone and \(\Phi_d\) is the flux reflected in the same directions by an identically radiated diffuser of reflectance equal to 1.
n3:plainTextDescription
Reflectance Factor is the measure of the ability of a surface to reflect light or other electromagnetic radiation, equal to the ratio of the reflected flux to the incident flux.