So, filming this on a c300 MKII, everything looked good enough.
However, once I brought it into Premiere/Media Encoder, it gave me this strange inverted look.
Using the Inverted (Channel: In Phase Chrominatic) effect cancels out the worst of it but still doesn't feel exactly right and I'd rather fix it organically than add effects. It's shot 1080 RGB444 12 bit using C Log 2 C.Gamut.
If you are running Premiere Pro 15 - this is a known issue. There is a cumbersome workaround available (search 'C300' in this forum). Maybe go back to Premiere Pro 2020 if you can when working with C300 footage until the bug is addressed.