FCP applies a gamma curve to all imported footage when using DV, uncompressed 8bit or uncompressed 10bit. Run your photoshop through a gamma filter. I saw the same problem when I transitioned from Media 100 to AJA/FCP.
Adam Wilt emailed me the following:
Try applying a gamma correction to the test patterns (it’s either 1.2222 or 0.81818; I forget which one you use in which direction off the top of my head. Chris Meyers says he uses 1.228 and 0.824, FWIW). You should be able to get everything back on target this way.
That should correct the problem.
-mark