Just a quick question: in the Final Cut Sequence Settings, under Video Processing, which option should be selected for Canon 5D Mark II footage?

Always render in RGB
Render in 8-bit YUV
Render 10-bit material in high-precision YUV
Render all YUV material in high-precision YUV

The third option produces artifacts in highlight regions - they become black.

Note that this is for 5D footage in ProRes (LT) format, with no effects aside from basic FCP filters.

Thanks.

I work on a laptop, so I tend to use the 8bit YUV option while I'm working for speed, then switch it to the 10 bit YUV mode when I create a master file. I've never seen the black artifacts you mention, I'm using ProRes standard though so maybe it's related to LT?