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half-value angle, <for a diffusing surface, by reflection or by transmission>


angle of observation at which the luminance has half the value of the luminance of the diffused light at the angle of 0°, with perpendicular incidence of the light

Note 1 to entry: For indicating the shape of the scattering indicatrix it is recommended that the diffusion factor, σ, be used for strongly diffusing materials, and the half-value angle, γ, for poorly diffusing materials.

Note 2 to entry: The half-value angle is expressed in radian (rad) or degree (°).

Note 3 to entry: This entry was numbered 845-04-90 in IEC 60050-845:1987.

Note 4 to entry: This entry was numbered 17-515 in CIE S 017:2011.

Publication date: 2020-12
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