lightSpectra: compute standard light spectra


Two families of standard illuminants that depend on temperature are the Planckian spectra (black-body spectra), and daylight spectra. For the daylight spectra, a smoothed version is available. Illuminant E, a third and trivial spectrum, is also available.


planckSpectra( temperature, normalize=TRUE, wavelength=300:830 )

daylightSpectra( temperature, components=colorSpec::daylight1964, 
                              wavelength=NULL, roundMs=FALSE )

illuminantE( power=1, wavelength=380:780 )



a vector of temperatures, in Kelvin


a colorSpec object with the daylight components S_0, S_1, and S_2. The default is daylight1964 and a smoothed version daylight2013 is also available.


a vector of wavelengths. For planckSpectra and illuminantE this is required. For daylightSpectra this is optional. The default wavelength=NULL means to use the wavelengths in components, and otherwise these wavelengths are resampled using resample


a logical value. If TRUE the Planck spectra are normalized to have value 1 at 560nm. If FALSE then the quantity returned is radiant exitance with unit W * m^{-2} * nm^{-1}.


a logical value. The original CIE method for the daylight spectra requires rounding intermediate coefficients M1 and M2 to 3 decimal places. This rounding is necessary to reproduce the tabulated values in Table T.1 of the CIE publication in References.


a vector of power levels


For daylightSpectra the valid range of temperatures is 4000 to 25000 K. For a temperature outside this range the spectrum is set to all NAs.

The equations for daylightSpectra and planckSpectra are complex and can be found in the References.

IlluminantE is trivial - all constant power.


For planckSpectra and daylightSpectra :
A colorSpec object with quantity equal to 'power', and organization equal to 'matrix' or 'vector'. The specnames are PNNNN or DNNNN for planckSpectra and daylightSpectra respectively.
The number of spectra in the object is the number of temperatures = length(temperature).

For illuminantE :
A colorSpec object with quantity equal to 'power'.
The number of spectra in the object is the number of power levels = length(power).


G√ľnther Wyszecki and W.S. Stiles. Color Science : Concepts and Methods, Quantitative Data and Formulae. Second Edition. Wiley-Interscience. 1982. page 146.

CIE 15: Technical Report: Colorimetry, 3rd edition. CIE 15:2004. Table T.1, pp 30-32, and Note 5 on page 69.

Schanda, Janos. CIE Colorimetry, in Colorimetry: Understanding the CIE System. Wiley Interscience. 2007. p. 42.

See Also

daylight, resample, organization, quantity, materialSpectra

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