I have done a few tests to ascertain if there is a better workflow for 4K files are produced by Sony and Panasonic camera
I have tried converting to Prores 422 and 422 HQ and I don't see any difference of any sort. Prores 422 is 492 mbps for my 25 fps files so around 5x the size and Prores 422 HQ is 737 mbps
It looks like the H264 conversion is not so strong to warrant the 422 HQ conversion as there is no difference with 422.
However the same files at HD seem to benefit from conversion to Prores 42 HQ from Sony XAVC 50 mbps
What I am getting at is that the new iMovie has Prores 422 as an output format so I am thinking that it is possible to process those files with decent result with the following steps:
- Import to iMovie directly from SD card
- Editing (no or minimal colour correction as the files are 8 bit)
- Export to Prores 422
- Encode to HEVC with handbrake
At the end of this process I get decent quality that looks very similar to the footage as it was captures with files that are around 25 mbps or 3 Mb/s so 3 minutes work out at 480 Mb which is not too bad
Unfortunately Youtube does not accept HEVC and Vp9 crashes when I try to create similar files. I have converted the same files to H264 high profile to youtube specified 35-45 Mbps and they look gross. I think this explains why many clips in youtube at 4K look not so great and full or artefacts
