Very, very few output formats preserve all 32 bits per channel. OpenEXR is one.
Just to be clear, though, you don’t need to output to 32bpc to get the advantages of working with 32bpc color within After Effects. I don’t know Final Cut Pro well, but I’d be surprised if there was any reason to try to get all 32 bits per channel from After Effects into FCP.
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Todd Kopriva, Adobe Systems Incorporated
putting the ‘T’ back in ‘RTFM’ : After Effects Help on the Web
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