I am making a showreel from previous projects which were converted into Quicktime files at 1280 x 720. The highlights of each project I am editing in MPEG stream clip and compressing to Quicktime (for the second time) in Apple Prores 422, then I will stitch together the separate Quicktime movies in FCP7.

The original footage is taken on a Panasonic AV HMC 152 and GoPro Hero HD.

How much am I compromising quality by doing this and is there a better way of doing it?

For the record, the finished compilation/showreel is unlikely to be shown on anything larger than a laptop screen.

I dare say the last step you describe as "Compression into Quicktime -Prores422" is for all intents and purposes an Uprez and not lossy.

When you export from FCP to a "Quicktime File" (not using Quicktime compression or Compressor), FCP gathers all the bits from the timeline plus the render files and assembles them together in either a standalone file or as a reference file depending what you choose. It keeps the video compressed in the same format so that's lossless as well.

So if you went from the camera native format into FCP into a Quicktime (camera native) File into MPEG Streamclip into Quicktime (Prores), I don't see much loss going on. However, if you did apply compression when you exported from FCP, then that quality is what's going to come out the end of this current effort.

Make sense?

That's pretty much what I was hoping to hear. Thanks again Les.

...And a Merry Christmas to you!

My experience lately is you should try and edit the footage without compressing it in Mpeg Streamclip first for best quality. I have a client who sends me mp4 footage which loses too much quality if i convert it first edit and then output. Sometimes I use the converted footage as a proxy so I can edit something and then go back to the original for conforming. My point is recompressing does show up and may bother you more than you think. Also using compressor with a reference file for output looks much cleaner than Mpeg Streamclip. Still use Streamclip but not if i am concerned about the output looking its best.