Re: keystone distortion cause

[P3D john bercovitz <bercov@xxxxxxxxxxx>]

I think if you check a book on view cameras, you'll find
that keystoning comes from not having the film plane 
parallel to the face of the object.  If the lensboard is 
tilted, the plane of best focus is not parallel to the 
film plane but I don't think you'll get keystone distortion 
from this.
 
In a stereo camera, the film gates are coplanar so 
keystoning matches in the two views for a non-parallel object 
face. 
 
John B


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