Photometric counterpart of radiance, producing the visual sensation called brightness. Typical units are: \(\pu{candela m-2}\) (\(\mathrm{nit}\)), \(\pu{candela cm-2}\) (\(\mathrm{stilb}\)), \(\mathrm{foot}\ \mathrm{lambert}\) (\(2.426\ \rm{nit}\)). 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, \(2042\ \rm{K}\)). Conversion from photometric units to radiometric units (e.g. \(\rm{J s}^{-1}\)) requires convolution over wavelength of the relative spectral response of the human eye (photopic response tables).