----- Original Message -----
From: "Mark Cassino"
Subject: OT: What Mount Is This?
> I recently picked up a Rikenon 100mm f2.8 on eBay, thinking it
was a
> K-Mount. It's actually a mount I've never seen before - the
lens is quite
> flat, has no aperture diaphragm, and has a "snout" that must
stick into the
> camera body. There are threads on the base of the snout, they
seem to be
> around 30mm in diameter.
>
> What type of body would this lens fit?
Your post doesn't mention the age of the lens, but about
30-40 years ago, many camera manufacturers made cameras that had
a semi-convertible lens system. There would be a rear lens
section, with aperture, and sometimes shutter (most times the
shutter was FP type) that was permanently affixed to the camera.
Interchangeable front sections were used for changing focal
length. I recall some of the Ziess models worked in such a way,
the early Contaflex's I believe were of this type.
Nikon used to have a semi-convertible telephoto, where one
purchased a rear section containing the aperture and a real lens
element set, and could purchase separately the front sections
for 600mm, 800mm and 1000mm focal lengths, if my memory serves.
Convertible lenses lave a long history in large format
photography also. I believe Komura still makes convertible
lenses for 4x5. Goerz Gold Dot Dagor convertible lenses are to
this day a much sought after lens for the large format
enthusiast. Unfortunately, Goerz was absorbed by Schneider in
the 1970's, and the Dagor lenses ceased production.
True convertible lenses use two symmetrical groups. Each
group can be used separately, or together. This gives the
possibility of three different focal lengths in a true
convertible lens. I call the Zeiss Contaflex type semi
convertible because while the front element was replaceable, the
rear was not, nor would work as a lens on its own. I suspect
that your Rikenon lens is for such a system.
William Robb
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