I recently purchased a 5D Mark III and I've been doing a ton of research on how to get the best quality out of it (short of hacking it with ML and shooting RAW). My preferred editing software is Final Cut Pro 7 and I've been looking into ways of exporting the footage only once; that is, for the final output.
My question is basically, is it possible for me to convert the footage to prores, edit it all, offline the footage, connect to the original files then export? I'm wondering if I'll get bad results because the sequence has to be set to an editing format so will that result in a loss in quality for the final export, or is that just so final cut has an easier time playing back the footage?
In the end, it's not a big deal as I know prores is a next-to-lossless format and considering all my content is generally for output to the web, it's going to get heavily compressed anyway. However, I'm just curious as it's always nice to understand the potential/limitations of my editing systems. I've got premiere which I suppose would be the easier solution, but 1. I'm not overly comfortable with it and 2. I don't have twixtor licensed for it which I use in every single one of my edits.
Try the free 5DtoRGB from the app store. If you want to batch the footage, there is a paid version called 5DtoRGB Batch. I'm a user of the software, that's my only affiliation with it.
I've found it does the best conversion to ProRes-- all flavors.
Why do you want to go back to the original h.264 versions? Once in ProRes, you are working in 10bit. It won't make you footage look better as 10bit, but any post processing you do such as FX, color correction, titling will benefit from being processed in 10bit.