Photometric counterpart of radiance, producing the visual sensation called brightness. Typical units are: \(\text{candela}\ \text{m}^{-2}\)(\(\mathrm{nit}\)),\(\text{candela}\ \text{cm}^{-2}\)(\(\mathrm{stilb}\)),\(\mathrm{foot}\ \mathrm{lambert}\) (\(2.426\ \text{nit}\)). 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, \(2042\ \text{K}\)). Conversion from photometric units to radiometric units (e.g. \(\text{J s}^{-1}\)) 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 (