[QUOTE=Dan Keaton;1229395]
An update to this subject:

What I've found is that indeed you can drop a 100 or even 160mbs long GOP nano/XDR QT clip into FCP and if you let the NLE auto-conform your settings to the codec *it thinks you're working with*, (wink wink) in this case XDCAM 50mbs 1080i 60, it will allow you to export without reconforming the GOP structure of the clip (i.e. recompressing) with the exception of the beginning 15 or 30 frames of an edit/cut. (assuming you did no other image manipulation except a cut)

Sorry, that's a long-winded way of saying it won't recompress the clip unless you're altering the image (CC, filtering, transitions, etc) or you have an edit point on the timeline, in which case it has to reconstruct the GOP at that edit point.

I did some extensive testing with one of my codec torture test clips and you could clearly see where the image had been recompressed to 50mbs XDCAM and where the original (uncompressed quality) clip was left alone.

Barlow

This is why my workflow includes getting the rough cut on the timeline in FCP and immediately using media manager to create new clips for me, in a new project. Either 10 bit Uncompressed or 10 Bit ProRes422 HQ. Once I have the new project, I'm confident that the quality will remain through compositing, color grading, etc.

You need to make sure you check "Delete Unused Media" in media manager though, otherwise it will export the complete length of your original clips.

Yup, I think rough cutting in an XDCAM timeline, and then using the media manager to transcode to ProRes for final edits/corrections/outputs, etc, is a great workflow. Much easier than converting everything to ProRes from the beginning. I think uncompressed 10bit is overkill for most anything though, especially if it's a lengthy project.