Re: [Leica] More fun w/Noctilux and M3

["Dan Post" <dwpost@email.msn.com>]

Chandos-
Might it just be wear of the locking lug? I used a Noctilux on my M3 for
months and never had a problem, in fact, it took me a while to figure out
what you guys were talking about!
I wonder if the replacement of the lug assembly is an option? It shouldn't
be that expensive ( compared to the cost of your Nocti, mere peanuts!) and
if the M4 lug components fit, and provide more security, it might be a good
idea to 'upgrade' it!
Dan
- ----- Original Message -----
From: Chandos Michael Brown <cmbrow@mail.wm.edu>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Monday, August 30, 1999 12:19 PM
Subject: [Leica] More fun w/Noctilux and M3


> Following my earlier posting about the "looseness" of the Noctilux on my
> M3, I spent a pleasant couple of hours fiddling around with both.  I offer
> a few conclusions based on the purely empirical nature of my research.  To
wit:
>
> Both the 50/1 and the 75/1.4 exhibit a similar propensity to uncouple from
> the M3.  Through repeated and accurate testing, I determined that there's
> enough play in the M3 lens flange locking mechanism to allow for lateral
> movement of the lens in the mount (rather than the rotating movement that
> mounts and locks the lens).  Often this movement (< .1mm) is sufficient to
> lift machined notch in the lens flange clear of the locking pin, which in
> turn, allow a minor rotation to loosen the lens in the mount.
>
> For the purposes of experimentation, I adjusted the height of the locking
> pin by shimming it w/ a bit of film-stock (it's tougher to describe this
> than to do it).  This modification dramatically improves the security of
> the lens.
>
> This accomplished, I thought to examine the degree of wear in the mount be
> comparing it with an M4P.  The 50/1 and 75/1.4 mount securely to the M4P
> with *no* play whatsoever.  What I notice immediately is this: the M4P
> mount was re-engineered precisely to correct this problem w/ the M3.  The
> M4P beefs up the lug directly beneath the locking pin, in effect,
> increasing the coupled lug-to-flange surface area of the lens/body mounts,
> which, in turn, prevents lateral movement in the lens.  The M3 relies more
> than the M4P on the spring tension of the mount to secure the lens.  I
> don't use an M6, but I assume that it incorporates the M4P design or some
> refinement of it.
>
> Preliminary conclusion:  while the M3 VF is wonderfully well suited to the
> Noctilux, I'm not entirely certain that the mount is robust enough safely
> to accommodate the lens.  I'm not going to stop using it, but I offer
these
> observations as a caution . . .
>
> Chandos
>
>
> Chandos Michael Brown
> Assoc. Prof., History and American Studies
> College of William and Mary
>
> http://www.wm.edu/CAS/ASP/faculty/brown
>