Why the requirement to pass an illuminant in the "colour.sd_to_XYZ" definition?

[hminle]

Hi Colour Team,

I have a question about how to convert spectral data to XYZ correctly.
In the sd_to_XYZ function, why we need to specify illuminant?
As I read from many other sources, we do not need to do that, right?
Just like this:

Source: color-matching-function

Thanks

[KelSolaar]

Hi @hminle,

If you look at the definition signature, it is an optional argument so it does not need to be passed and will default to CIE Illuminant E, equivalent to multiplying by 1.

Cheers,

Thomas

[hminle]

Oh thank you so much @KelSolaar . But for other cases, that illuminant argument is for viewing condition, right?