Methods for Re-defining CIE D Illuminants
CIE D illuminants, and proposes two methods to smooth the daylight illuminant
spectral power distributions. The first method keeps the values originally determined
at the integer 10 nm intervals unchanged and interpolates between these fixed points
to get smooth (twice differentiable) curves (minimal smoothing method). A second
alternative method smoothes more strongly, cutting fine structure maxima and minima
of the spectrum (highly smoothing method).
Examples show the consequences of both methods, pointing out that smoothing has
little influence on colorimetric accuracy.
The Technical Committee recommends testing the provided tables based on the two
smoothing algorithms in practice and to urge users to test data of Table 4 which are
based on the highly smoothing method, and ask instrument constructors to test the
method for building D illuminant simulators with the eventual outcome of defining a
CIE D50 and D65 standard source.
The publication provides a link to two Excel files: one for calculation of the SPD of a
daylight illuminant for the different interpolation methods described in this report after
input of a required CCT and another one providing the tables of the report .
The publication is written in English, with a short summary in French and German.