index of sensation, M

[5.9.11.5.5]

(of a source)*

A number that expresses the effects of source luminance (L_s), solid angle factor (Q), position index (P), and the field luminance (F) on discomfort glare rating, where L_s and F are expressed in cd/m².

M = (0.5 L_s Q)/(PF^0.44)

See solid angle factor, Q for an equation defining Q.

* Levin RE. Position index in VCP calculations. Journal of the Illuminating Engineering Society. Jan 1975;4(2):99.