# 17-21-103

reduced luminance coefficient

r

luminance coefficient multiplied by the cube of the cosine of the angle of incidence of the light on a point on a surface

Note 1 to entry: The reduced luminance coefficient can be expressed by the equation
r = q (cosε)3

where q is the luminance coefficient in steradian to the power minus one (sr−1), and ε is the angle of incidence in degrees (°).

Note 2 to entry: The angle of observation, α, affects the value of r. By convention this angle is fixed at 1° for road lighting calculations.

Note 3 to entry: The reduced luminance coefficient is expressed in steradian to the power minus one (sr−1).

Note 4 to entry: This entry was numbered 17-1046 in CIE S 017:2011.

Publication date: 2020-12