Quote Originally Posted by Anon Ymous View Post
Parallelogram, or did you really mean trapezium?
The most common misalignment should produce that.

Can you misalign an enlarger and get a rhombus
from a square frame?
Well you mentioned "the parallel sides" in your post
so I went with that. Rhombus, trapezoid, from the
four sides of the negative I can't say how many
quadrilaterals might be formed.

I've an Issue of Camera and Darkroom wherein
an article describes a method of alignment which
makes use of the trapezoid as part of the
alignment procedure. Dan