for what it is worth, I up-converted our entire 80 minute feature length production (shot in 720/24p) to 1920×1080 by doing the following:
duplicate your project but define the resolution as 1920×1080 (as opposed to having it set by the first clip of the project) and do not duplicate by copying over rendered files. This will cause your project to be re-rendered at 1920×1080 in FCPX. I then exported the file using Apple ProRes 422 HQ.
I then took this file and had it transferred to HDCAM. The film showed at the Hawaii International FIlm Festival and at the Los Angeles Asian Pacific Film Festival in theaters, and while there was a bit of resolution loss, it looked fine to me (of course, it was mu child, why wouldn’t it). I continue to search for better methods. You can download Davinci Resolve Lite for free, that can also do this, but I noticed no difference and indeed thought FCPX did a slightly better job.
In the end, as I am learning, it is best to shoot in 1080. My issue was long days in the field with one camera with a single 64 GB P2 card, not to mention the hard drive purchases to hold all the 1080 footage. But when you are a guerrilla filmmaker, something usually has to give…
Jack Niedenthal
Microwave Films of the Marshall Islands
http://www.microwavefilms.org
https://www.microwavefilms.org/Crickets.html
iMac i7 using Mountain Lion 10.8.x, HPX 170 using only one 64GB card
I live on an island in the middle of the Pacific, YOU are my only resource.