[Leica] LTM & Enlargers

[Marc James Small <msmall@roanoke.infi.net>]

Your query concerning the use of the LTM on enlargers to the Large Format
List was reproduced on the Leica Users' group.  Allow me to respond.

Oscar Barnack, the chief designer for Leitz, worked with Hugo Meyer and an
English camera shop to develop the Leica thread-mount.  This eventually
ended up as 39mm by 26tpi, the latter being, I understand, in Whitworth
thread though, fortunately, I've never had to cut such a thread on my
Unimat.  The reasons for this specific selection are now unknown:  I have
spoken with several folks who knew Barnack personally, but none ever asked
him this question, and, in any event, it does not seem to have been
documented in the surviving Leitz/Leica records.

The specific thread and pitch were determined in 1931 and were patented.
This patent expired in 1951, though the Orientals and Soviets pirated the
mount before this date.  (Canon and FED both got it wrong, at first, but,
eventually, came to understand that Barnack MEANT 26tpi and not some metric
equivalent.  Hence, early FED gear from the '30's, and Canon stuff from the
'40's, will occasionally bind in a true LTM.)

Leitz marketed enlargers which used this thread to allow the use of the
solid 3.5/3.5cm Leitz Tessar taking lens as an enlarging lens.  This began
in the early 1930's.  By the middle years of that decade, Zeiss Ikon was
adapting their range of enlargers to allow this practice.  After the end of
the Second World War, Leitz marketed adapters which allowed a swathe of
bayonet-mounted lenses to be used on their enlargers.

The basic answer is that Leitz used the LTM on their enlargers to allow
taking lenses to be used as enlarging lenses.

I hope this answers your query.  If not, ask on!

Marc

msmall@roanoke.infi.net  FAX:  +540/343-7315
Cha robh bas fir gun ghras fir!