White balance uses sRGB as reference sometimes causing autoWB failures

[Beep6581]

Originally reported on Google Code with ID 2115

White balance (colortemp.cc) uses sRGB as reference, and (possibly) due to that auto
white balance sometimes fails in underwater images etc due to multipliers becoming
negative. Perhaps keeping the sRGB reference while doing some special handling for
out-of-gamut white balance could work?

Reported by torger@ludd.ltu.se on 2013-12-09 17:41:43

[Beep6581]

@Desmis

1. Does white balance (colortemp.cc) still use sRGB as reference?
2. Does Auto-ITC handle underwater shots better than the old auto-WB?

[Desmis]

@Beep6581 It is a convention to use srgb(D65) as reference for conversion xyz Some years ago, someone, I don't remember who, ask for changing that... I objected, because - even its a convention and perhaps (???) be better with Prophoto - its work very well with sRGB. No importance to have negatives values in RGB

But the big, huge difference is in calculations, now all is made with spectral datas (illuminant, color, observer)

No Itcwb does not work at all for underwater, it's not a daylight illuminant. That's why I maintained old auto grey WB

Jacques