Quote Originally Posted by Lee L View Post
However, your statements about measuring color temp with only blue and red, disregarding green are simply wrong, and misleading.
Astronomers measure color temperature with Ultraviolet, Blue, and Visible (green-yellow) passband filters, that don't reach deep into red. And yes, they do use green wavelengths as a component to measure color temperature. That's where the V component filter peaks in sensitivity.
I also wrote and taught curriculum for physics labs on color temperature at a top ranked college...
You should recognize that there is more than one way to measure color temp, and that stating that it's always and only a blue-red ratio is wrong.
You'll forgive me for presenting an answer that's relevant specifically to photography.

This is after all a photography forum, not one for astronomers or physicists.

Since you appear to be well-versed in the theory, you should know that the "color temperature" of any visible black-body spectrum can be calculated by comparing the amplitudes at any two points on the curve. Accuracy is enhanced by choosing two points that are as far apart as possible in wavelength (i.e. color).

It's convenient and less expensive from a manufacturing standpoint to measure red and blue components and compare them. This DOES NOT include green, which is measured separately if at all.

We're dealing with visible light here, with CT in the range roughly 2500 to 6500 k.

Photographers don't care about UV.

- Leigh