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).