Archived posting to the Leica Users Group, 2000/05/14

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Subject: [Leica] rangefinder adjustment - long
From: Rick Dykstra <>
Date: Mon, 15 May 2000 10:55:37 +1000

I think it was John Collier who wrote or found the following in the archives:
> There are two places to adjust: first, the eccentric screw on
> the roller; and second, the eccentric on the rangefinder arm pivot.

Hi folks.  On the topic of rangefinder adjustment .....  

It's one thing to calibrate the lens to the rangefinder, but it would be
nice to know that the subject is then focussed on the film plane. To
check that, a focussing screen resting on the film guides is needed.
More on this later.

When I look through the lens mount of an upside down M6, I see three
slotted screws. The following describes what I think they're for.

The screw closest to the lens mount supports a roller that rides on the
lens' cam as the lens is focussed. This screw appears to be
eccentrically mounted on the rangefinder arm. Turning this screw would
adjust the relationship between the lens' cam and the rangefinder. This
looks like the screw for fine adjustments to the way the rangefinder
reads the lens' cam.

The second screw in from the lens mount holds the rangefinder arm onto a
swivelling pin that descends from the optical unit.  Between this
screw's head and the rangefinder arm is an eccentric washer, that itself
sits within a recess of the rangefinder arm.  I see two possibilities
here.  If this second screw was partially tightened, then the eccentric
washer, upon being rotated clockwise, would serve to hold the arm in the
right place before the screw is fully tightened.  On the other hand, if
the rangefinder arm has a slotted hole, then the eccentric washer could
be rotated to lengthen or shorten the extension of the rangefinder arm
from its pivoting point.  I think the former of the two possibilities is
the correct one.  This second screw and the eccentric washer look like
they're for rough setup adjustment of the rangefinder, with the
eccentric roller screw (the first screw) being for fine adjustment.

The third screw in from the lens mount is also surrounded by an
eccentric washer. Lying against the washer is a metal arm with a twist
in, held by and pivoting from the second screw.  This arm comes into
contact with the third screw's eccentric washer when the rangefinder arm
moves all the way forward, such as when the lens is removed. Loosening
the screw and turning the washer would adjust the forward most limit of
the rangefinder arm's movement, and might protect other elements within
the rangefinder system from being knocked around when the lens is

So, if an M6 rangefinder does not show correct focus when the lens is
focussed at the film plane, to my way of looking at those screws, its
the first screw, the one with the roller, that should be adjusted.  I'd
leave the other two alone.

A while back someone on list pulled from the archives a description of
how to bend a pair of slotted screwdrivers for this adjustment job.  One
ends up with the screwdriver tip in line with the right angle bend and
the other with its tip square on.  Someone else recently mentioned that
the arm should be supported when the roller screw is being adjusted. The
adjustment itself - trial and error!

In making an adjustment, one could either set the lens to infinity and
adjust the rangefinder to suit, accessing from the back with the lens
attached if feeling confident.  Or, focus the lens on an object up close
by viewing a focussing screen sitting against the film guides and then
take the screen away, stick the screwdriver in from the back and adjust
the rangefinder to suit.  Leica workshops have a jig, a lens and I think
a focussing screen for doing the latter.  With the adjustment done for
up close focussing, intermediate and infinity focussing is then
assessed.  If the rangefinder is out at infinity, then it would appear
to be the lens that's at fault.  Uh oh.

How does all that sound?  I'll stand by while you get to work with your
screwdrivers. On your cameras! Or, send 'em to me and I'll have a go. 
So far, mine haven't needed adjusting, but you can see I'm looking
forward to the day that they do!


Rick Dykstra