Archived posting to the Leica Users Group, 2001/08/07

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Subject: [Leica] R8 aperture control ring malfunctioning
From: Ray Moth <ray_moth@yahoo.com>
Date: Tue, 7 Aug 2001 21:29:15 -0700 (PDT)

Dear All,

Well, it seems that a problem I reported to the list a month ago,
concerning the DoF lever on my R8 getting jammed if I pressed it too
far down, is worse than I thought! I did some experimenting, yesterday
evening, to see whether lens irises are able to close fully to their
smallest aperture if I press the DoF lever only as far as the point of
resistance, i.e. not far enough to make it jam. I found that they are
sometimes able to close down fully but will often stick before getting
to that point, i.e. the spring in the lens is not strong enough to push
the aperture control ring in the camera, reliably, to its farthest
extent. 

Worse than that, I found there is also a problem when taking a shot
using the shutter button. The aperture to which the lens closes is
unpredictable and varies from shot to shot. It seems worse at apertures
smaller than f/8. The R8's aperture control ring must be binding and is
too stiff to be overcome, reliably, by the spring in the lens. I found
that it can be helped (if the shutter speed is long enough, say, 4
seconds) by tweaking the DoF lever several times, which can nudge the
aperture control ring a bit and allow the lens to close down to the set
aperture. 

I had the R8 in manual mode, BTW, so automatic aperture selection (as
in P and T modes) didn't enter into it. I experimented with four
different R lenses and had the same problem with each one, so the
camera is definitely to blame. It will have to go back to Leica :-(

Olympus OM cameras operate the oppposite way to Leica R, that is, the
lens is sprung internally to be fully open until it is forced to close
down by a lever (not a ring) in the camera. I would think this design
must be mechanically faster and more reliable than the ring arrangement
in the R cameras. 

The way R cameras control the aperture seems odd to me, relying on a
fairly weak spring in the lens to move a large aperture control ring.
There is very little time for the iris to close down during the
shooting cycle and any stiffness or sluggishness in the aperture
control mechanism will likely lead to incorrect exposures, at apertures
wider than those actually selected (except, of course, when the largest
aperture is selected). I'm surprised that more R owners haven't
reported aperture control problems.

Regards,

=====
Ray

"The trouble with resisting temptation is
 you never know when you'll get another chance!"

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