This article is from the rec.arts.movies.tech FAQ, by Scott E. Norwood snorwood@nyx.nyx.net with numerous contributions by others.
Although it is not a 16mm shooting format, 16mm reduction prints of
35mm anamorphic original films are often printed in a 2:1 squeeze
ratio, which retains the original side framing, but crops off a small
portion of the top and bottom of the frame. Projection of these films,
obviously, requires an anamorphic lens for the projector in order to
`unsqueeze' the image. Almost all 16mm anamorphic prints are
reductions from 35mm anamorphic originals.
 
Continue to: