Just tried mixing 4K and 1080 in multicam. Wanted to be able to "punch in" on 4K shots after cutting multicam. But issues no matter how I try setting up the multicam (4K or 1080). (That is, yes you can do it, but not with total flexibility.)
Anyone got this working successfully? Again, want to be able to use different sizes of the 4K cam in a 1080 master timeline, via a multiclip. And, 2nd camera angle in multicam is 1080 only.
My current workaround is syncing the clips in multicam, then grouping into a compound clip for editing. This allows clips to retain their native rez. Not great, but I don't have a lot of content to deal with, so workable.
OK, I was editing in a student cafe at my daughter's college when I made the OP, so maybe not the best venue for critical thinking. ;)
Turns out I overlooked the frame rate - the mult clips were set for 24, not 23.98. That seemed to be the culprit in making the mult viewer wonky/smearing/etc.
Also found that, in casual comparison, there appears to be no degradation in image quality when using either a 4K or 1080 multicam into a 1080 timeline, and then scaling the 4K image back up to native size (for a punch-in). So the image processing pipeline appears to go from native file -> final output, without intermediate processing.