For what it's worth, my old Sony Z1P HDV would white balance down to 23m (pointing it at the palm of my hand). Sometimes I would need to point it at the sun to get a fix if I was close to the depth limit. I was happier with the Z1P underwater manual white balance results than I have been so far with the GH4, but I haven't shot a lot of available-light stuff yet. It's difficult to say exactly what bothers me about the GH4 u/w white balance. The footage might just be lacking saturation, especially in the blue water. It's not that bad though.
p.s. I could manually white balance my VX2000 at 50m (in available light with a blue-water filter)!
I found all the MWB results really good.
Since it was not my camera I didn't want to mess much with image configuration and it is true that I found the image a little bit unsaturated but when I went to color grading.... great behavior!!!.. contrast, saturation with no artifacts. It is also tru that I will have to upgrade my computer because 4K really slows down the whole post-production chain!!!!!
- Nick Hope likes this