[Leica] 'cron 50mm DR on M8

[pklein at 2alpha.net (Peter Klein)]

As Frank said re. the 50mm DR 'Cron:

>It is identical to the one of its era {meaning the Rigid Chrome Cron. 
>--Peter}.  There have been a 2 or 3  evolutions since, though I would need 
>to look it up to be sure.
>Frank

The lens heads of the DR 'Cron and the Rigid 'Cron are optically identical 
in terms of design.

My idea was to get a mount from a 50mm chrome "Rigid" Cron with bad glass, 
which might be obtainable cheaply. Screw out the lens head of my DR, screw 
it into the Rigid mount, and I could use my DR lens head on the M8 without 
having to buy another whole lens.

Problem #1:  The Rigid 'Crons' focal lengths vary slightly, due to 
manufacturing tolerances of the time.  Leica actually made different mounts 
to match the various minor deviations in focal length.  All DR crons, on 
the other hand, have exactly the same focal length.  So I would have to 
find a mount that matched the DR's focal length.  There are ways to 
tell--the exact focal length is scratched or penciled onto the inside of 
both the lens head and the mount in a shorthand that's been published.

Problem #2:  DAG told me that the above won't work because the DR and Rigid 
mounts are "different."  However, someone on here:
http://www.l-camera-forum.com/leica-forum/leica-m8-forum
reported that he could screw his DR lens head into a Rigid mount, and he 
says it focused perfectly.  But the f-stop marker ended up pointing 
sideways rather than upwards.  Sounds kind of iffy to me.

Based on that, the ways get the DR "look" on the M8 would seem to be:

- Have your DR altered so the close focus cam no longer hits the inside of 
the body in normal range.  It will now work on either the M8 or a film M in 
the normal range.  But it will never have its close focus range 
again.  You've lessened its resale value.  According to some Leicaphiles, 
you've committed desecration.  According to some practical cats, you've 
done the most economical thing.  Remember, your 90mm lens at its closest 
normal focus gives you almost the same field of view that your 50mm DR does 
in the close-up range., and you don't have to mess with goggles.

- Get a DR with bad glass cheap, have the mount altered, and use it with 
your good DR lens head for the M8. You still have your original mount with 
close focus for film.

- Buy a Rigid for use on the M8, or buy another DR and alter it.

- If you can get a Rigid with bad glass cheaply, it might be worth the 
experiment to see if it focused your DR head.  But remember to determine 
whether the mount matches your lens head's focal length before you buy 
it.  Your mileage may vary.

--Peter