(of a source)*

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

M = (0.5 LQ)/(PF0.44)

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, 10th ed. (IES 2011).


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