"Dag Korsnes" writes:

I thought a "normal" lens giving the same field of view or magnification as
the eye on 35 mm SLR was about 57 mm, not 50 mm. For some reason 50 mm has
become the standard "normal" lense (except on some old Praktica).

The usual definition of a normal lens is one with a focal length equal
to the format diagonal. By that measure, the normal lens for a 35 mm
camera is 43 mm FL. There have been some 45 mm normal lenses included
with cameras, but 50 mm is most common.

Minolta used to have 57 and 58 mm "normal" lenses. I think the
rationale for these was that, when used with the viewfinder
magnification of their cameras, they gave nearly 1X angular
magnification (i.e. "life size" viewing in the finder).

Dave