I've seen a few threads here about video exported from FCP X (Share->Export Media...) then opened in Compressor being noticeably darker (both viewing and exporting). I started noticing the same thing about two months ago. I've tried tweaking the Gamma, Brightness, and Contrast settings when exporting from Compressor but have not found the magic combination to just retain the same look as in the FCP X timeline. Someone mentioned using Share->Export Using Compressor Settings... as a workaround - and it works! The videos come out looking the same! So far, so good.
However, there is one glitch. My Custom settings created in Compressor aren't available in that menu in FCP X. It shows the Custom folder, but says it has 0 items, when it really has 7. I CAN successfully use those custom settings from within Compressor itself. My understanding is that those Custom settings are supposed to be available from that menu - any ideas as to what would make them not accessible?