Im trying to find out how i can import a quicktime file from FCP in AE for color correction then render it back out to the same frame size and ratio. at the moment when i open it back up in FCP its not the same.
the file from FCP is
Pixel aspect PAL-CCIR 601
Just import your footage into AE then drag the footage into the New Composition icon at the bottom of the Project panel. It's the third icon from the left. Kind of looks like a little frame of film.
This will create a new composition that is exactly the same specifications as your original render from FCP. Make sure that the footage is properly interpreted for Interlacing issues, and if it is interlaced make sure that have the proper interlacing setup in the output module. Depending on your codec you may also want to turn on Match Legacy Gamma in the project settings.
You shouldn't have to worry about any other settings.