Calculate luminance (cd/m2) and related quantities (lux,lumens,cd) from spectral
energy
lum = ieLuminanceFromEnergy(energy,wave)
Purpose:
The CIE formula for luminance converts a spectral radiance distribution
(W/m2-sr-nm) into luminance (candelas per meter squared, cd/m2). This
routine accepts RGB or XW (space-wavelength) formatted inputs. In XW
format, the spectral distributions are in the rows of the ENERGY
matrix.
The formula for luminance and illuminance are the same, differing only
in the units of the input. Hence, this routine calculates illuminance
(lux) from a spectral irradiance distribution (W/m2-nm). It also
calculates luminous intensity (cd) from spectral radiant intensity
(W/sr-nm); finally, it calculates luminous flux (lumens, lm) from
spectral power (W/nm). The pairings are:
Luminance: cd/m2 from W/sr-m2-nm
Illuminance: lux from W/m2-nm
Luminous flux: lumens from W/nm
Luminous intensity: cd from W/sr-nm.
To calculate luminance (or illuminance) from a spectral radiance
distribution in photons, use ieLuminanceFromPhotons()
Examples:
wave = 400:10:700;
energy = vcReadSpectra('crtSPD',wave)'; %Note transpose
energy = [1,1,1]*energy;
lum = ieLuminanceFromEnergy(energy,wave)
Online reference:
http://www.optics.arizona.edu/Palmer/rpfaq/rpfaq.htm
Copyright ImagEval Consultants, LLC, 2003.