The Leica Rangefinder and the importance of a well calibrated system – By Alan Starkie

The idea of the rangefinder is simple, it’s an optical triangulation device coupled to a cam on a lens. Align the two images in the viewfinder and the camera is in focus. People put a lot of trust into the Leica cameras; the camera works smoothly and the viewfinder and rangefinder are bright and clear and focus onto infinity – in fact the rangefinder unit contained within is probably the most complex of any camera.

Coupled with some very expensive lenses, a Leica rangefinder camera should be capable of producing some very sharp shots shouldn’t it? Not necessarily….

The lens

Within a lens, there two things that are important to ensure correct focus. Firstly, the RF coupling cam should be accurate and second, the optics should be correctly collimated. Generally, it is unusual for there to be any error in the RF cam. In other words, when the lens is set to infinity, the position of the cam usually agrees but it can be out occasionally.

What I do find quite regularly though, is that some lenses focus a little past infinity. This is a problem with an RF camera because shooting at infinity with such a lens, no matter how good it may be, at any aperture will produce exceedingly poor results. At closer distances this shouldn’t be a problem but it’s worth mentioning.

On lenses with goggles there is an additional complication. The goggles themselves have to be precisely calibrated. I was checking a goggled lens earlier on today with a camera with a good rangefinder. At infinity all was well but at 1 metre, the rangefinder was 5cm out. This would be immediately spotted on an SLR but one would not expect that of a Leica. I had to drill out and replace a grub screw to fix it.

The camera

As far as the camera goes, many people know how to adjust the rangefinder within a Leica M camera. You have the large slotted screw on the rangefinder arm which is on a concentric. This allows for horizontal adjustment. Behind the small screw near the illuminator window is a screw that allows vertical adjustment (later cameras need a special tool for this). Most repairers or the DIY owner will make the horizontal adjustment for infinity but on ‘M’ cameras there’s a third adjustment that I call linearity.

When the camera has been correctly set up, there is an imaginary line on a graph that intersects the 1m point and infinity. If this setting is wrong – as it usually is, the rangefinder may be perfectly set to infinity but as the subject gets closer to the camera, accuracy diminishes at an increasing rate. The third adjustment is found just under the smaller screw that attaches the RF arm to the camera.

A number of iterative adjustments are required between close focus and infinity to get this right. So what? You may say. In most cases it probably doesn’t matter too much, but when so much has been invested in a camera and probably even more for the exotic lenses that go with the system, an inch or two focus shift when focussing on the sitters eye could leave the photographer very disappointed with the result.

With something like a SLR, what you see is what you get. It’s extremely unlikely that the focussing screen would be out of alignment and even a badly collimated lens would be automatically corrected by the visual focus confirmation in the viewfinder.

The conclusion

So, the lens cam has to be right. The lens collimation has to be right. The rangefinder needs to be correctly adjusted so that the camera accurately focusses through infinity and down to 1m and below. Any lenses with supplementary goggles need to be correctly set in addition to the lens itself. I suppose in most cases these things go largely unnoticed. General photography, street photography etc where precision is less important than ergonomics.

It reminds me of a comment made by Leitz management during a visit by British and American officials, post WWII to Wetzlar, where it was noticed that slow speeds on production line cameras weren’t particularly accurate. Leitz acknowledged this but pointed out that “however, … the results obtained were quite good enough for all general requirements.”

I don’t wish to portray this as a bad camera, not by any means. The trouble is that like a Ferrari, everything has got to be just right in order to get the performance and there are many small things that can go wrong that wouldn’t be obvious when using the camera. Of course, this isn’t blaming the camera. Correctly set-up, all should perform well, but the nature of the system means you have to put your trust into it.

Thanks, Alan – CameraWorks-UK

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18 thoughts on “The Leica Rangefinder and the importance of a well calibrated system – By Alan Starkie”

  1. I would pretty much call this Leica bashing. By the way: any source about Leitz management and their good enough standards? Because this is exactly what German camera‘s are known for: low technical standards and lack of reliability?!

    1. I’m not sure it’s Leica bashing. It’s pragmatism from a well known and well regarded Leica repairer. I suspect Alan has forgotten more than most of us will ever know about the internals of these cameras.

    2. Leica bashing? Don’t be so thin-skinned. They’re not perfect and recognition of this fact only leads to greater understanding of them. I thought Alan’s comments well worth the time taken to read them.

  2. You are right comparing Leica to a Ferrari. If everything works fine it is a amazing tool
    to work with but like every tool you have to check it by service from time to time.
    It is not the case that it works precefctly over decades and there is n, mistery about it at all.

  3. There is no mechanical device working perfectly over decades. Even a tank needs maintenance. It is nice and important to know that cameras need maintenance and that there are qualified people dealing with them. Wether this makes them a Ferrari, Porsche or T34 I do not know – I keep those things separated. For as long as you use your tools you will notice once they need a check up – I never ever trusted in any of my cameras: I just use them and send them in once they develop some quirks.

    So nothing is unfailable, not even a Leica. I can well live with that.

  4. When my father worked for Nippon photo clinic, he remembers squeezing the leica m shell too hard while adjusting the RF, and it would also drift. All mechanical objects have limitations, it’s the results that count

      1. Hamish, KR only shows the f2.8/35 Summaron with spectacles or “goggles” as this is needed for the M3. Leica aficionados know of the verson for the f2.8/135mm Elmarit-M, a beast of a lens. With the M3 having frame lines for 135mm and there being other 135mm lenses in the line-up, why spectacles for the M3? Well, it assists with focusing the lens more accurately via the rangefinder. The rangefinder spot is magnified making it easier to check that the superimposed images is spot on, felt more necessary with the more limited dof of the f2.8 aperture.

        1. Indeed, I was just giving an example. As I understand, the 135mm lens with goggles also brings up 90mm lines, but magnified

  5. George Appletree

    There are probably several ways of criticizing Maserati.
    For example you could argue is a car for idiots. But that would be bashing (not actually the brand but the users).
    With Leica would be the same.
    Anecdotes like “however, … the results obtained were quite good enough for all general requirements” maybe are acceptable if you get a camera from 1930, but not a brand new one, specially if expensive.

  6. Unlike a single lens reflex camera, where the end result can be previewed in the viewfinder, one has to trust that things are correctly set up correctly, otherwise results may be disappointing, especially where subjects require critical focussing. This is related more to correct maintenance and adjustment than the Leitz name itself. The quote “quite good enough for all general requirements.”, was made during a visit by British and American officials sometime after the end of WWII and the report produced by British Intelligence Objectives Sub-committee (Para.36) The document makes very interesting reading for anyone interested in some of the more technical historic aspects of the Leica and a copy can be found on Peter Grisaffi’s website here:

  7. Of course, users of digital M’s can employ the Visoflex EVF to check accuracy of the viewfinder and use it for critical focus since the image is generated directly off the sensor. While you may lose the joy of working with a viewfinder camera, the EVF does serve a useful purpose. Some longer lenses such as the 135 Apo-Telyt can be almost impossible to critically focus using the viewfinder, even one perfectly adjusted.

  8. Pingback: What is a Rangefinder Camera, and is one right for you? - 35mmc

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