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[frohnec]

I have a Kalart side mounted rangefinder. The arm that extends from the squared knob to the round keeper on the slide is off.
Where should this be on the front side of the keeper on the rail so that when the rail comes out it pushes the arm counter clockwise?


[ This Message was edited by: frohnec on 2004-05-13 15:47 ]

[t.r.sanford]

The chances are that you will need to adjust the Kalart rangefinder when you get the arm back on. There is an essay elsewhere on this site that describes how to do that.

This said, the desired geometry of the arm is such that:

-- when the lens is run out against the "infinity stops" on the track

-- and focused sharply on an object at infinity (Kalart said 500 feet or greater distance; the "Focal Encyclopedia of Photography" suggests 1,000 feet)

-- then the follower mounted on the track is holding the arm back (thus rotating the moving prism in the rangefinder) to precisely the degree that causes the two images of the object visible through the rangefinder to coincide, to merge into one image.

Note that the arm rides behind, not in front of, the follower.

As you've probably observed, the pivot that carries the arm is spring-loaded. The spring presses the arm forward, gently, against the follower.

The arm's ability to rotate is constrained by the mechanism, so that when you focus forward beyond the closest position the rangefinder can measure, the arm stops as the follower continues to move forward.