Re: [Leica] M BODY CAP

[Kip Babington <cbabing3@swbell.net>]

Bill -

I thought you might have had a defective cap, as I have several of these
older caps, and both lock positively into place on my Visoflex.  But I just
tried them on my M6 and only one of them engages the lens lock.  (I assume
you've noted that there is only a single notch in the plastic rim at about 9
o'clock (looking from the front) that engages the lens lock, unlike on the
plastic Minolta caps which have 4 notches and so lock on no matter which way
you start them.)

The viewfinder frames, and the preview lever, are actuated by the 3 o'clock
lug on a lens (again, looking from the front).  The various lenses have lugs
that either don't engage the internal mechanism at all (35/135), part way
(50/75),  or all the way (28/90).  Your body cap has lugs that will move
this mechanism, and the preview lever, if rotated clockwise far enough past
the locked position, but my plastic cap will do the same thing if you hold
the lock button down to let it go past lock.  This is just doing what a lens
does when mounted, so shouldn't do any harm to the frame selector
mechanism.  If you also hold the lock button in when mounting a 35mm lens,
for example, and rotate it a bit beyond where it would normally stop, you'll
start to bring up the 50/75 frames.  I don't know if there are tight spots
on the bayonet channels of the lens mount that shouldn't be invaded this
way, so I don't do it on a regular basis, but have tried it occasionally (in
the spirit of scientific inquiry) over the years with no visible harm to any
of my lens mounts.

BTW, one of my older caps is from my days of owning both an M3 and M5 at the
same time.  On the M5 the meter arm dropped out of the way when the lens was
removed, but the old style metal-backed body cap would engage the frame
selector (as you've noted) and raise the arm at least part way to the
operating position.  Since power was cut off to the meter arm when it was
retracted (as it was before each exposure, or when a lens was removed) but
could be supplied by pressure on the shutter button once the arm was in
working position, I took my handy Dremel tool and ground off the leading
corners of the lugs on my body cap to be sure that it wouldn't engage the
meter arm no matter which position it was installed in (the underlying metal
is brass, so this was not very hard work.)  As I recall, this idea for
modifying the body cap came from something I read from Leica at the time,
not something I just made up.  And I gather that the cap locking lugs were
redesigned at that time to keep from activating the meter arm.

Cheers,
Kip

Bill Satterfield wrote:

> I have one of the old M body caps with the metal back. It came on my M3.
> Why will it not click into place and why does it move the lens preview
> lever if rotated a little too far? The present body cap does not do
> that. Will it harm  the camera?