Soviet rangefinders calibration clue ?

[ruben bitt]

On the old manual of a Fed 2 (Butkus, our voyage guide to knowledge) I have found an interesting statement, saying that if we know the distance between the photographer and the subject, better you use the rangefinder distance scale. And if you do not know,then use the range finding method.

You may understand from it that the classic yellow patch, the classical range finding method is not the most accurate for the best possible sharpness, or at least for the Fed 2. But this is not my concern, whether it is true or not.

The interesting point for me is that according to this statement, the highest Supreme Court to the right distance is in the camera distance scale.

And this may sound obvious for some, but wait a moment. I knew, we all know, that in order to check a Soviet rangefinder metering, distance scale, yellow patch, and actual distance, should all be the same, all in agreement, otherwise something of the three is wrong.

But when I went every time to make the adjustment, I never knew the distance scale will beforehand determine the distance, something that can be easily checked, and the yellow patch is the one that should be corrected. Rather I have used the actual distance first, to align the yellow patch coincidence, instead of checking to death the distance scale, and then arranging the yellow patch.

All these may sound obvious again, but the fact is that when you align the three, some small disagreements do happen, sending you to a slight compromise. The core of the problem is, in my opinion, that the yellow patches are not highly, highly, accurate. I.e. our vision is good enough to appreciate the superimposition of the images, but this superimposition if judged by severe ways is not perfect. And this natural imperfection may or may not influence an f/1.5 shot. Therefore, the yellow patch is to be calibrated as the last instance, what may look in sharp superimposition, may not be in fact as sharp as it may seem to be. It is the distance scale the one that not lies.

Hence why the Fed 2 manual is giving me a lead to proceed when calibrating. This clue is applicable only to those rangefinders with at least a 180 degree lens rotation (the Kievs have more)

 

[darkosaric]

Hi,

Some time ago I was reading on the Internet about focusing accuracy and base length for Leica M - there one can see why yellow patch is considered not to be 100% accurate.

 

[Xmas]

Hi Ruben

Unless you are confident that the previous repair person adjusted the registration plate for the lens accurately you need to do that first?

Noel

 

[ruben bitt]

Folks, I am talking about the possibility that there is certain margin from what we see as a correct superimposition and the accurate one, had we perfect sight. I am talking about our eyesight of a perfect-from-the-factory calibration.
Think about the following: the slr focusing method takes some more time to focus, but you have there a split image screen. The range finding method is much more easy and fast, but may have it flaw exactly there, it is done by our eyesight of the superimposition. By definition this superimposition although perfectly calibrated from the factory, may be not as accurate in the field as the slr split image screen because it depends more on our capability to see it in a highly accurate way than the slr split image line. Of course that the wide baselength is a good medicine
I am not sure about the Fed 2 manual comment, it is rather my speculation, but there is some logic there. Or perhaps their starting point is that Feds they manufacture are built with unaccurate calibrated yellow patches.
- Noel, the other day I was looking the amount of 50mm Kiev lens I have, and the actual shooting bodies. It seems I have trashed some 7 cameras by trying to clean, or adjust them :munch:

 

[ic-racer]

It is also curious that the lenses of these cameras (and Zorki also) have exact lines for the focus scale numbers.

 

[snapguy]

age

Well, how old is your camera? Is it just possible that it is not in perfect shape like it may or may not have been when brand spanking new? I suggest your camera is probably unique to itself and that perhaps bangs and whacks and drops it experienced over the years may have thrown a lot of things out of perfect whack, so to speak. And you need to determine what this particular camera will do, not what the brand/model is supposed to do.

 

[georg16nik]

On the old manual of a Fed 2 (Butkus, our voyage guide to knowledge) I have found an interesting statement, saying that if we know the distance between the photographer and the subject, better you use the rangefinder distance scale. And if you do not know,then use the range finding method.

You may understand from it that the classic yellow patch, the classical range finding method is not the most accurate for the best possible sharpness, or at least for the Fed 2. But this is not my concern, whether it is true or not.

The interesting point for me is that according to this statement, the highest Supreme Court to the right distance is in the camera distance scale.

And this may sound obvious for some, but wait a moment. I knew, we all know, that in order to check a Soviet rangefinder metering, distance scale, yellow patch, and actual distance, should all be the same, all in agreement, otherwise something of the three is wrong.

But when I went every time to make the adjustment, I never knew the distance scale will beforehand determine the distance, something that can be easily checked, and the yellow patch is the one that should be corrected. Rather I have used the actual distance first, to align the yellow patch coincidence, instead of checking to death the distance scale, and then arranging the yellow patch.

All these may sound obvious again, but the fact is that when you align the three, some small disagreements do happen, sending you to a slight compromise. The core of the problem is, in my opinion, that the yellow patches are not highly, highly, accurate. I.e. our vision is good enough to appreciate the superimposition of the images, but this superimposition if judged by severe ways is not perfect. And this natural imperfection may or may not influence an f/1.5 shot. Therefore, the yellow patch is to be calibrated as the last instance, what may look in sharp superimposition, may not be in fact as sharp as it may seem to be. It is the distance scale the one that not lies.

Hence why the Fed 2 manual is giving me a lead to proceed when calibrating. This clue is applicable only to those rangefinders with at least a 180 degree lens rotation (the Kievs have more)

Fed 2 RF patch is adjustable horizontally and vertically, same as on the Leica.

You can check the RF patch and lens scale accuracy and if they are in sync by removing the back of the Fed 2, placing a ground glass on the film rails and by using a magnifying glass, focus the lens on some previously checked distance targets. You might wanna draw a cross or series of horizontal and vertical lines with different thickness on a piece of paper, place it @ 1, 5, 10 meters and then use something far away as a infinity target. Then if something is not in sync; there are numerous how-to's with detailed pics gravitating around the net on how to adjust the RF patch, shim the lens etc..
Unless you are shooting a lot at very close distances, under 3 meters and with wide open lens, then most minor inaccuracies are better left alone, better shoot some film and spend your resources in creative direction.