[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.

* Note: A restatement of this formula lends itself more directly to computer applications.

See also The Lighting Handbook, 10^th ed. (IES 2011).