Paul J Gans wrote:

I dimly recall the term "prime lens" as being the
lens whose focal length was equal (at least roughly)
to the diagonal of the film frame. That made a 50mm
(or 45mm) lens "prime" for 35mm film.

The usual term for this is "normal lens"


A 135mm lens was then a "telephoto" and a 35mm lens
was a "wideangle".

A telephoto lens, properly speaking, is one in which
the lens (when set to infinity focus) is closer to
the film/sensor than the focal length of the lens.

It is quite possible to have a wide angle lens
which is of telephoto constuction. Olympus compacts
have had such lenses for years. On an Olympus XA,
the point 35mm in front of the film is actually
just in front of the front element of the lens.

A lens which is significantly longer than a normal
is called a long-focus lens if it is not of telephoto
design.

Wide angle lenses for SLRs are generally of an
inverted telephoto type in which a point one
focal length in front of the film may be somewhat
behind the rear element of the lens.

Peter.
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