[Cory Andrews] “Compressor also thinks the film is 16:9 when it’s actually 4:3.”
[Cory Andrews] “I edited with is 1920X1080”
Your movie IS 16:9, the image within that space maybe 4:3 but you are editing 16:9.
What was the framerate of the 16mm, what pulldown method did they use. For best quality the pulldown should be removed to get the footage back to progressive.
You cannot judge quality of the video within FCP, you need an external monitor to see what you actually have. If you can only use FCP’s canvas it has to be set to 100% or else it is throwing away 1/2 the scanlines which is why it finds a lot of these type of problems.