5D3, ADTG2 and ADTG4[0x8, 9, A, B]:
- at first sight, these seem to be some black biases: in LiveView, they will cause vertical lines in shadows, but there is a filter that will adapt to the changes fairly quickly (seems to be a moving average).
- at a closer look, changing this register also affects the gain, and we can lower the ISO a little bit more (noise gets lower and there is some more highlight detail captured). Initial guess: 0.15 ... 0.25 stops (maybe more if there is nonlinearity, I don't know yet).
- I believe these are the registers Greg was playing with on 500D.
Will try to update the research tools to the latest codebase today.