IES LM-37-20

This document’s methods of calculating average luminance cover various open-bottom apertures as well as flat- and drop-lensed units, including those with multiple openings in the light emitting area. The candela values of interest are obtained by means of IES techniques for relative or absolute photometry, and are not obtained from field measurements in application. This calculation is based solely on the candela values obtained by goniometric measurement of the luminaire and the luminous projected area. All light sources for which there are current standards for luminaire photometry are covered by this document. These include incandescent, fluorescent, high intensity discharge (HID), low pressure sodium, and LED sources.