reduced luminance coefficient (for a point on a surface) [r]

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

Unit: sr-1

NOTE 1 This can be expressed by the equation

         r = q (cos ε)3


        q is the luminance coefficient in sr-1;

        ε is the angle of incidence in °.

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

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