Much of the F3 look is due to a 1080p imager and recording in ProRes, the combination gives a dreamy soft image with little compression posterisation i.e better tonality.
If you want to recreate the look of the F3 in the FS7 you can by shooting 4k using some fairly heavy lens diffusion and at the end of the project output in HD. This was my recipe for getting the very best 1080p image out of the FS7. I found this looked much more organic than shooting internally at 1080p which suffered from too much sharpening for my taste.
Not sure why you're referencing pro-res for the F3 - unless you're specifically talking about external recorders. F3 has always been XDcam 420 internally. Though the last film I shot with my F3 (Girl On The Train - 2013) we recorded s-log externally in 444 uncompressed -- and in testing during preproduction decided that a little extra softening (slight black pro-mists) provided us the look we were going for. I still really like the look and colors from the F3 - and continue to use it for several of my clients.


