I have been reading all the various posts about H264 gamma shifts all morning. Here's my workflow:
Shoot on 7D DSLR and Sony Ex-3
Convert the DSLR footage to Apple Pro Res
Edit in Final Cut 6.06 in an Apple Pro Res timeline. (Ex-3 footage gets rendered in timeline.)
Everything looks beautiful.
Export full res. quicktime file with current settings.
Everything still looks beautiful.
Compress to H264
Now the shots that were originally from the EX-3 still look beautiful, but the shots from the DSLR are washed out, low saturated color.
I can get the DSLR shots to look beautiful again by adding a gamma correction filter of 1.2, but that makes the shots from the EX-3 way too dark.
Incidentally, I'm using a Matrox box for the H264 compression, but I have tested without it and get the same results, so I don't think that's figuring into the mix.