Photometric counterpart of radiance, producing the visual sensation called brightness. Typical units are: candela m −2(nit),candela cm −2(stilb),foot lambert (2.426 nit). As with all photometric quantities, luminance does not refer to a specific wavelength, but applies to light emitted by a standard source (formerly a 'standard international candle', now a blackbody radiator emitting at the temperature of solidifying platinum, 2042 K). Conversion from photometric units to radiometric units (e.g. J s −1) requires convolution over wavelength of the relative spectral response of the human eye (photopic response tables).
PAC, 1990, 62, 2167 (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2199