masking? like black borders? they need to be close to work. I don’t know exactly what you got, but the displacement map
could be created by hand by visually comparing parallax. white is closest and black is furthest, to keying, masking, or
even a precomposed difference matte.
I still don’t understand how they scanned it so wrong, even if it were another angle, AE’s Corner Pin effect should have worked no problem. also, the Lens Compensation effect should have fixed the focal length(if there was any). Until I see a screenshot, this one’s got me stumped.