To be clear:
* IncrementalTemperature and IncrementalTint apply only to RGB photos.
* Temperature and Tint (proper) only apply to raw photos.
But as you've noticed, Lr "hides" the values until White Balance has been "customized".
of course if white balance is already set to 'Custom' then the temperature and tint will be available (theoretically - unless done very recently and not yet settled).
If white balance is set to 'As Shot' or 'Auto' (and temperature and tint are not available, since never customized) then you can determine temperature and tint by setting white balance mode to custom, then waiting for the values to settle.
That last part (assuring values have settled) may be a bit tricky.
If white balance is set to anything else, then the values are fixed, so you know what they are, even if not available as named members.
Thanks much. I didn't realize the difference between Temperature and Incremental Temperature.
I suspect the theory is:
if rgb, some white balance has already been baked in, so the 'Incremental' prefix means "added after baking".
whereas in the case of raw it's an actual temperature in kelvin, and the tint is, well, relative to neutral or something..
Somethin' like that, maybe...
That makes sense.