Just adding to this that when I edit on a 4k timeline and output to 1080p, I get a much better resolution 100% crop as compared with editing on a 1080p timeline. Moral - edit on a timeline set to the source, not to the target.
This is the route I'm going at the moment, except my footage was shot at 4k cinema not UHD. What is the best way to get this resolution in a 1080 timeline in premiere without losing any of the image? (or FCP I'm guessing it doesn't matter much)
