Colour correction characteristics
I recently changed to a Fuji X-T3 and am shooting 25p UHD video in F-Log, HEVC 420 10-bit at 200mbps. Cin-GG doesn't seem able to fully cope with it. Let me try and explain.
Cin settings are Preferences/Appearance BT709, JPEG. If I import 3840 x 2160 10-bit and apply Videoscope the first thing I find is, if I set Format to RGBA (FLOAT or 8 Bit) the waveform monitor shows highlights clamped at 100 and they look severely burned out. If I set Format to YUVA-8 Bit only the highest peaks hit 100 with little clamping and only the very brightest highlights are burnt out. It doesn't matter which CC effects I use, it still happens to some extent.
Think fluffy clouds and the myriad of shades from brilliant white to relatively dark grey and I am missing the gradation in the higher shades. This does not happen in, for example, Shotcut or Kdenlive.
There are 3 Fuji LUTs one of which is F-Log to BT709 and if I use that it exascurbates the highlight problem a little. I can achieve a reasonably good highlights correction (in YUVA-8 Bit) with or without the LUT if I use Brightness/Contrast to pull the maximum level down to 95% then use either Colour 3-Way or Histogram and Hue Saturation. If I achieve decent highlights, I get noise in some shadows. Again it does not happen in the other NLEs. It looks the same whether in the Compositor window or in the player when rendered in ProRes.
I wanted you to know because, unless I am doing something wrong, there appears to be a mismatch in Cin.
"I wanted you to know because ... there appears to be a mismatch in Cin."
Maybe true, but GoodGuy and I do not have the expertise to definitely corroborate or to modify Cinelerra code accordingly. I believe this same issue was mentioned awhile back and GoodGuy attempted to understand it and studied the code in detail but this did not result in any conclusion. We are computer people rather than video/camera people and especially lack knowledge in the fine points of Color Correction, clamping, and Videoscope usage, etc.
However, there is always the possibility that an expert with programming skills will show up and help out in this area in the future.