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.)

where:

The *S _{n}(λ)* distributions are provided as a spreadsheet in ZIP format.

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

**Implementation Notes:**

- This equation is often used in a
*relative*form, normalizing so that*S*is 100 or 1.0 at λ = 560 nm._{D}(λ)