I have some footage in FCP, (1280x720) of an astronaut shot against black fabric.
I need to cut her out and composite her onto a starry background (of outer space).
So I exported uncompressed TIFF files and then intend to import them in to an AE project.
What composition setting in AE should I use? The 720p one is HDV and I thought that might be too compressed since my final out put from FCP will be Pro Res 422.
I thought I would export the final comp in to FCP as uncompressed TIFFs, so will that ignore the HDV colour space/compression of the composition setting?
Also, when I bring by still images in they do not run consecutively, instead are placed one under the other. How do I get them to run sequentially?
The settings you choose for your composition in the beginning of a project determine the size of the frame, the pixel aspect ratio, the frame rate, but not the final compression of the render. That is determined by the settings you choose from the render module.
It would help you to do a bit of reading on some basics for AE. Importing file sequences.
As far as compositing stars behind the astronaut, I would just use a garbage mask with a slight feather to eliminate the stars over the character and comp the star layer on top using Add or Screen, or even Unmult.