Spectral Power Distribution of a CIE D-Illuminant

The relative spectral power distribution of a CIE D-Illuminant is computed from its chromaticity coordinates. (The chromaticity coordinates may be computed from the correlated color temperature as described here.)

Equation 1

where:

Equation 2

The Sn(λ) distributions are provided as a spreadsheet in ZIP or SIT format.

You can use the CIE Spectral Display Calculator to see plots of the D-Illuminant curve at any temperature.

Implementation Notes:

  1. This equation is often used in a relative form, normalizing so that SD(λ) is 100 or 1.0 at λ = 560 nm.