Unidentified Leica Equipment

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Thank you, Stuart.

 

The rub is, of course, that it's difficult to tell the merely plausible from the truth.

[luigi bertolotti]

I think the mirror is there to let the operator observe the two dials at the same time. Am I mistaken or are the numbers on the dial within the apparatus printed so that they can be read in the mirror?

 

The instrument within the apparatus seems to measure the position of the arm which couples the lens to the range finder. The axis of the upper (horizontally arranged) instrument appears to be tangential to the lens mount. I think it might serve to sense the rotational position of some part of the lens, possibly the optical assembly. If so, the device possibly might be used to adjust the optical elements within the barrel to the proper distance from the film plane.

 

It's all iffy, of course, since the innards of the apparatus can not be discerned.

 

That's an interesting hipotesis, Philipp, alternative to what I speculated in one of my my previous posts : but... how do you explain what, imho, is a clear evidence : I mean, the fact that the scale of one of the indicators has a clear relationship with the distance scales of Leitz RF lenses ? It is the main element that makes me think of checking of the lenses' RF cam (together with the "mockup" of the Leicas' rangefinder roll, which appears in the first picture) : after all, the positioning of glass elements within the barrel (a critical element, to check/adjust, indeed) isn't related, per se, with the focusing distances (they weren't yet times of the floating elements... )

Edited October 30, 2014 by luigi bertolotti

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That's an interesting hipotesis, Philipp, alternative to what I speculated in one of my my previous posts : but... how do you explain what, imho, is a clear evidence : I mean, the fact that the scale of one of the indicators has a clear relationship with the distance scales of Leitz RF lenses ? It is the main element that makes me think of checking of the lenses' RF cam (together with the "mockup" of the Leicas' rangefinder roll, which appears in the first picture) : after all, the positioning of glass elements within the barrel (a critical element, to check/adjust, indeed) isn't related, per se, with the focusing distances (they weren't yet times of the floating elements... )

 

Please forgive me for repeating the obvious. Not being quite sure of the terminology, I have to make sure that my thoughts properly mesh.

 

In order to focus you have to move the optical elements of the lens to the proper distance from the image plane. As you write, the distances between the individual bits of glass are fixed; it is the whole assembly of optical elements which has to move forwards and backwards within the barrel.

 

In a correctly adjusted lens the distance between the image plane and the "central" plane of the lens is exactly the focal length when the distance is set to infinity. That is, of course, the definition of the focal length.

 

I presume the apparatus shown in this thread is used when inserting a freshly assembled optical system into the barrel. You have to ensure that the optical system is placed at the proper distance from the mount. Hence, you measure two distances: the displacement of the RF arm and the distance of the optical element assembly from the flange.

 

The scale on the lower instrument with the markings as found on the lens barrel make it simple to see whether the scale on the barrel, the coupling mechanism and the RF all agree about the distance selected on the barrel.

 

You need, however, to measure the distance between the "content" of the barrel, the optical elements, and the flange; otherwise, you will have a lens with front or back focus. That's what the second instrument in front of the apparatus does.

 

If I have understood the device correctly.

 

You use it, then, thus: You insert the assembly of the optical parts into the barrel, mount it on the apparatus, set the lens to infinity, measure the distance between the optical assembly and the flange using the front instrument, insert some shims or adjust some screws until the distances match; then you adjust the whole lens to a different distance, check on the lower instrument whether the RF arm agrees, then check wether the optical parts are at the proper position for the distance selected on the barrel, adjust again or replace the helicoid or whatever needs to be done.

 

That would explain the weight of the whole thing. You would not want to use your third hand to keep it from moving about on the bench while doing all those things to the lens.