The limits of the Optical Rangefinder

[scsambrook]

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There has been much discussion on the accuracy of focusing with the Leica M8 and M9. It is clear that some cameras sometimes show rangefinder errors at different distances, and that some lenses sometimes fail to couple correctly even on a camera with a rangefinder which is “correctly” adjusted. A variety of reasons have been proposed as accounting for these problems. In general it appears that focusing errors result from

1. A failure by the operator to align the rangefinder images correctly

2. Inaccuracy of the rangefinder’s calibration

3. Inaccuracy in the focussing mechanism of the lens

and, of course,

4. Combinations of points 1, 2 and 3.

 

The problems of achieving consistently high levels of accuracy with optical rangefinders were well known long before they appeared in 35mm cameras. Military and naval rangefinders all gave problems in use. Even using telescope eyepieces of 15x and higher, image-alignment errors by operators were common, and instruments employing moving image systems were notorious for providing inconsistent readings even when “correctly” adjusted in the factory or workshop. Shock, vibration and temperature fluctuations all affected both the accuracy and regularity of results – a rangefinder might work fine at one time but not at another, and then function correctly again without adjustment. I wonder to what extent might such operational inconsistencies lead to periodic variables in focusing accuracy with the M8 and M9 which are, perhaps wrongly, ascribed to other specific faults with camera body or lens?

 

 

Perhaps the time is coming for the maker to look for, or sponsor the development of, a suitable adaptation of electronic technology that will provide a viable alternative to the Leica’s complex, costly and relatively delicate optical rangefinder. The periodic debates over “wish lists” for the camera that must inevitably succeed the M9 all assume that the optical rangefinder must, perforce, remain as an essential part of the design. But consistently precise manual range measurement – which essentially is what really lies at the heart of the camera’s functioning – could conceivably be done with greater accuracy and reliability by an alternate method based on technology which already exists.

 

Periodically, both Ernst Leitz GmbH and Leica Camera AG have had to reinvent the Leica. The M3 represented almost as much a break with tradition as did the M8 (the M9 is but a refinement of the M8, after all). Both cameras represented new philosophies and were responsible for extending and invigorating the Leica camera’s appeal to a wider customer base. No matter how well the M9 is selling this year, it will not continue to do indefinitely and its production life will, of necessity, be relatively short in a consumer society which looks for both incremental and radical innovation. The M9 is really a “bridge” camera whose most expensive component, the optical rangefinder, is simultaneously its greatest strength and its weakest link. I suggest that we should start to accept that the optical rangefinder in the Leica is approaching the end of its days and that a third, major, re-invention of the camera is inevitable.

[efix]

As long as that third re-invention you see coming works similar to and is as much fun as using a rangefinder, and as long as current M-mount lenses remain compatible, I'm okay with that.

 

But despite all the things that "can" go wrong with a rangefinder camera - it is still one of the most elegant and enjoyable ways to take pictures, and rangefinder lenses continue to be the most well-crafted lenses in the world, providing some of the best image quality available for 35mm photography.

 

You know, there is a saying: "Never change a running system". It has some truth to it ...

[jaapv]

Well, given that my rangefinder on the M9 is consistently correct, only needs adjustment after a hefty bang and that all my errors are operator error tells me two things - Any other system is well into the diminishing returns and thus redundant and it would be a kind of idiot-proofing I would not want on my camera, as I don't like being replaced by a foolproof automaton - I prefer my own errors.

[bill]

You missed out one factor, although it could be argued it comes under heading #1 - the Leica rangefinder is wholly dependent upon both the quality of the user's eyesight and upon their ability to centre their eye on the eyepiece. It is further dependent upon them correctly interpreting what they are seeing and pressing the shutter release at the right time. I do wish more people would ensure that their vision is 20-20 and that their technique is sound before blaming the tool for their poor results.

 

Regards,

 

Bill

[lars_bergquist]

If the rangefinder is ever replaced with an electronic system, it will be because –

 

(a) The new system extends the range, or

 

( it is cheaper to produce.

 

Let us hope and pray that it will be reason 1. But frankly, knowing how a capitalist market works, we have reason to fear reason 2.

 

The old man from the Age of Scale Focusing

[jaapv]

I remember the same type of arguments being made in the 1960ies for automobile wheels and tyres being replaced by a hovercraft-type car-street interface.

[Steve Ash]

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Practice of many are proving that your assumption are mainly theoretical and does not affect many. I do not claim that there is not anybody who needed to service the camera as you suggested. But your posting give the false impression or falsely tries to imply that there is a inherent problem in the design which requires factory adjustment on any regular basis. This does not correspond to my experience at all despite heavy use of my gear in all kinds of environments. My cameras and lenses are spot on since years.

 

Regards

Steve

[Xmas]

Hi

 

I'd suggest the OP needs a Canon or Nikon DSLR, e.g. Nikon lenses are better then Leica lenses (sorry guys) so he would not lose anything.

 

The primary problem with a range finder with 'auto focus' is (or was) how to indicate what the camera has focused on, short of leaving the optical system as it is for focus confirmation, the Contax G1 and G2 had a mechanism but it was short on utility.

 

The second problem is the auto focus delay and here the Contax G2 improved the G1 to a degree, still unusable for me, I take up 1st pressure on the analogue shutters, to reduce any delay as much as possible.

 

The OP can get a X100 if he wants...

 

It is easy to appreciate if you buy a superspeed lens you are going to have serious problems with depth of field wide open, suggesting that it is the cameras fault tusk tusk. The f/1 (Noctilux 5cm) lens in '75-79 era had some similar bad press.

 

Leica should have realised that they were going to have problems with depth of focus of the digital sensor and lens focus shift, from their f/1 history. Commercial pressures probably...

 

Noel

[lct]

...I suggest that we should start to accept that the optical rangefinder in the Leica is approaching the end of its days and that a third, major, re-invention of the camera is inevitable.

Which re-invention actually? Laser rangefinder? So far the optical rangefinder we know is the unique way to focus a ... rangefinder. Other ways like EVF have nothing to do with rangefinders and are far from being as fast and accurate as the latters. Further improvements could come from a higher VF magnification and/or a longer base of the rangefinder though.

[Paul Verrips]

The M9 is really a “bridge” camera whose most expensive component, the optical rangefinder, is simultaneously its greatest strength and its weakest link. I suggest that we should start to accept that the optical rangefinder in the Leica is approaching the end of its days and that a third, major, re-invention of the camera is inevitable.

 

If thats your opinion, fine. Move to another system.

 

You have no M blood running through your veins.

[Xmas]

If thats your opinion, fine. Move to another system.

Hi Paul

 

I'd have suggested another fora myself you are way too nice.

 

Noel

[pico]

[...]Perhaps the time is coming for the maker to look for, or sponsor the development of, a suitable adaptation of electronic technology that will provide a viable alternative to the Leica’s complex, costly and relatively delicate optical rangefinder. [...]

 

Delicate? That's a merely impressionistic impression.

 

And what alternate technology would you suggest? Be careful. We have some real engineers, research & design people here.

 

No matter how well the M9 is selling this year, it will not continue to do indefinitely and its production life will, of necessity, be relatively short in a consumer society which looks for both incremental and radical innovation. [...]

 

Speak for yourself.

 

Personally, although I am soaked in high tech every day, I don't belong to the Change for Change Sake (AKA: disruptive technology) camp or Bleeding Edge.

 

Most of the errors I find in rangefinders are operator errors.

[Jager]

The tide of commentary - of which I entirely agree - is clearly against the premise here raised. Sorry Scsambrook.

 

I'll only offer, in addition, that the rangefinder is the very heart and the soul of the M system. It is much more than just a way to focus the lens. It is the way you see the world - through a window instead of through a tunnel.

 

And that fundamentally changes the ethos of how you capture life around you.

[cernobila]

Just a question, but first........last time I used the M3 was about 30 years ago when my sight was good. I can not remember if the viewfinder had optical adjustment for those that wore optical glasses. (at that time this was not an issue for me)

 

For today's past and present M cameras, because you have to place the camera against your eye.......for those that have to wear glasses......how does this work out, is there optical adjustment as in SLR/DSLR viewfinders?

[pico]

Just a question, but first........last time I used the M3 was about 30 years ago when my sight was good. I can not remember if the viewfinder had optical adjustment for those that wore optical glasses. (at that time this was not an issue for me)

 

For today's past and present M cameras, because you have to place the camera against your eye.......for those that have to wear glasses......how does this work out, is there optical adjustment as in SLR/DSLR viewfinders?

 

I have what my optometrist in my town of 30,000 people calls about the worst case of astigmatism in the area (about 20/200 vision with cylinder abberations I cannot understand) and I have been a Leica (and other brand) photographer for over fifty years.

 

My vision cannot be corrected to 20/20. But I manage a Leica M very well.

 

I'd be quite happy to compare my focusing ability against those who claim the Leica rangefinder is deficient. My bet is that it is the problems are largely operator issues. Not Leica optics at fault.

[underground]

DUDE! WT*

[adan]

Several points:

 

First, you missed numbers 4, 5, and 6

 

4. magnification of the viewfinder.

5. lens focal length

6. lens aperture.

(7. Combinations of 1 through 6.)

 

All of these are factors in whether a given user and a given lens can be focused with a given camera by a given user. The Leica RF has a "fixed" precision, that does not change with the lens used (unlike the SLR approach, where the lens provides its own increasing precision as the speed and aperture increase) so those factors matter.

 

I have 20/50 vision without my glasses, and can still focus my M9 (.68x magnification) with a 35mm f/2 lens in about 0.5 second. The .68x accuracy or precision for that lens and aperture is vast overkill. Getting the images even vaguely aligned is good enough.

 

The same is not true for longer fast lenses - I do need my glasses for, say, the 75 f/1.4 or any of the 135s. Which is, of course, why Leica doesn't make RF-coupled lenses longer than 135mm - and did, at varying times, make higher-magnification viewfinders (M3 and M6/7 .85x and accessory magnifiers (none of which I use).)

 

When you mention calibration problems, all you are saying is: if it's broken, it doesn't work anymore. Well - duh! The same will apply to whatever magical replacement system you are suggesting. It won't work if it is broken.

 

Do you actually have stats as to how often Leica RFs and/or lens calibrations are "out" - or are you just going on anecdotes?

 

To go further, you use a lot pf premises which you state as fact - that I don't think are actually factual. I'd like some evidence that:

 

"There has been much discussion on the accuracy of focusing with the Leica M8 and M9." - How much? - and what is "much?"

 

It is clear that some cameras sometimes show rangefinder errors at different distances, and that some lenses sometimes fail to couple correctly even on a camera with a rangefinder which is “correctly” adjusted. - Any premise with that many "somes" in it is not "clear" at all. How much is "some?" 1%? 10%? 2.3546%?

 

"In general it appears that focusing errors result from..." - You missed half of them the first time around - how many more did you forget?

 

"The problems of achieving consistently high levels of accuracy with optical rangefinders were well known long before they appeared in 35mm cameras." - Evidence?

 

"Military and naval rangefinders all gave problems in use.... (et seq.)" - Evidence?

 

"The periodic debates over “wish lists” for the camera that must inevitably succeed the M9 all assume that the optical rangefinder must, perforce, remain as an essential part of the design." - Actually, many of them do not. Live-view and EVFs are trotted out all the time as suggestions.

 

I could go on - but essentially every single thing you state as axiomatic truth, I do not think is factually accurate. Although I have an open mind if you have evidence.

 

Put bluntly, you make what the law calls an "argumentative" case. No evidence, just opinions framed as fact.

 

I was on a jury last week. The Prosecution had far more evidence than you've presented - and we still voted "Not Guilty" on all counts.

[lct]

...you missed numbers 4, 5, and 6

4. magnification of the viewfinder.

5. lens focal length

6. lens aperture...

7. length of the rangefinder base

[Xmas]

The problems of achieving consistently high levels of accuracy with optical rangefinders were well known long before they appeared in 35mm cameras.

 

It is easy to detect when some one has a degree in sophistry, they normally start out with a false or meaningless sentence, and then reason from there...

 

In '79 Leitz suggested one of the problems perturbing focus with the Noct f/1 could be that the camera lens registration distance might be out, so any body send back for rfdr adjustment would have all parameters checked. This is less critical for the 5cm lens, more so with the shorter focal lengths. So we should add another term/item

 

8) lens/body registration

 

But one of the important things withthe current rfdr is

 

With a pre M4-2 camera you can set up the rfdr with a star (for infinity), calibrated tape measure, and screw driver... post M4-2 you need a special tool. But or and you should check the rangefinder regularly, star or moon should be spot on, even if it is at the wrong end of the focus range... if it is out you need to adjust...

 

Noel

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