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Backfocusing lenses. Is it a Leica-only disease ?

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It usually shows when you can rotate the lens further than the overlapping rangefinder fields on a far away object, causing double contours again. If it is the camera, it is a one- minute user adjust, if it is the lens, the correction is rather more complicated, like adjusting the registerdistance of the mount and/or helix.

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It usually shows when you can rotate the lens further than the overlapping rangefinder fields on a far away object, causing double contours again. If it is the camera, it is a one- minute user adjust, if it is the lens, the correction is rather more complicated, like adjusting the registerdistance of the mount and/or helix.

 

I have a 35/1.2 and 50/1.5 Nokton which exhibit this but in my case it's not a cause for concern. When the camera rangefinder shows coincidence on a distant object the object is in focus with both lenses. It's just that the mechanical stop on the lenses is set fractionally past infinity.

 

Bob.

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A true rangefinder attitude, Bob

The results count...

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It usually shows when you can rotate the lens further than the overlapping rangefinder fields on a far away object, causing double contours again. If it is the camera, it is a one- minute user adjust, if it is the lens, the correction is rather more complicated, like adjusting the registerdistance of the mount and/or helix.

 

Thanks. I may test this on my 50 which seems to have the most issues with possible backfocusing. Are they related?

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E Puts pointed out that Zeiss has designed its current lenses with the assumption that film will bow backward, while Leica's assumption is that film will bow forward.

I was wrong in the above comment. In fact, I had the matter backward. I had misremembered Herrn Puts' comment in comparing the ZM and Leica lenses:

 

http://www.imx.nl/photosite/comments/c016.html

In theory you want the true focus plane to coincide with the location of the film plane in the film gate. But the true (or paraxial) focal plane does not necessarily give you the best overall contrast at a target of let us say 20 lp/mm. All ZM lenses had an adjustment in the minus direction, which is in front of the film plane. The Leica lenses were adjusted to the plus side, that is behind the (theoretical) film plane. From these figures it is clear that Zeiss assumes that the film surface is bulging outward, where the Leica designers assume that the film is curved inwards, or at least that the optimum location is in the emulsion layer and not slightly forward.

 

In addition, Peter Branch had already made the point correctly in regard to Leica designs at http://www.l-camera-forum.com/leica-forum/leica-m8-forum/29355-backfocusing-lenses-leica-only-disease-2.html#post307185.

 

--HC

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It usually shows when you can rotate the lens further than the overlapping rangefinder fields on a far away object, causing double contours again. If it is the camera, it is a one- minute user adjust, if it is the lens, the correction is rather more complicated, like adjusting the registerdistance of the mount and/or helix.

 

thats exactly what happened to me today. my brand new 75 cron is not going to mongolia (i am) because it focuses "beyond infinity" and will be ready in a month or so. oh well.

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Misha--

Maybe you should take the lens along. You might be able to get it repaired under way. I understand Leica has been hiring a lot of Mongolian technicians recently.

 

--HC

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I have had my M8 for 3 weeks. I thought I had been spared of the backfocusing as my 24, 35 cron and even my 75mm summilux were sharp on! Recently I took some pictures with my 50 Asph lux (LHSA version) to realize it backfocuses. At very close distance the focus is accurate, but beyong it backfocuses badly (several feet behind the focus point). Now even with my M6 I had never been thrilled by the sharpness of this lens. It is under passport so I guessI have to return to Leica NJ.

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I know I've read about this problem before but can't find the reference. What's the best way to tell if your lens is not focusing correctly on infinity?

 

Stephen,

 

Jupiter makes a very handy bright, extremely distant object. Take two photos, one with your rangefinder images exactly overlapped and one with the lens wound as far round as it will go, both with lens wide open. You will obviously need a sturdy tripod and use either the self timer or a remote release. Whichever photo is sharper will tell you if it is the camera or the lens which need adjusting. If you have another longish lens (50mm or longer), cross check with it. As others have said, adjusting the infinity is a one minute job with a 2mm hex key. I find mine needs fine tuning every month or so anyway.

 

Wilson

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Misha, if your camera is focussing correctly with two lenses, adjusting the rangefinder to work with your 75/2 will inevitably upset the alignment for the other two lenses. As Jan says, all lenses and all cameras need to be calibrated independently of each other to defined standards to ensure any lens works with any camera.
When I was in Solms in June , i was told that for really critical focus adjustments they would need the specific lens and body together. I used the same logic. The camera has to be right first ..then you can adjust each lens to the factory specification. Otherwise you don t have truely interchangable bodies and lenses. The response I got was that the can set the camera up for critical focus with the longer lenses (75/90) but that might night be best for the 28/35.

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When I was in Solms in June , i was told that for really critical focus adjustments they would need the specific lens and body together. I used the same logic. The camera has to be right first ..then you can adjust each lens to the factory specification. Otherwise you don t have truely interchangable bodies and lenses. The response I got was that the can set the camera up for critical focus with the longer lenses (75/90) but that might night be best for the 28/35.

 

 

Roger,

 

If that is the case and not an excuse to explain poor sloppy workmanship, it undermines the whole concept of an interchangeable lens, rangefinder camera or a Leica one anyway. It will be interesting to see, as and when Zeiss bring out their digital Zeiss Ikon, with its longer rangefinder base, if it suffers from the same problem. I am guessing it won't.

 

Wilson

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Does anyone know how Leica actually tests for focus accuracy ? It seems that some problems with the camera get sent to "Quality Control" which I believe means the factory. I can understand that beyond a certain point ..factory equipment would be required. i.e. rangefinder repalcement, sensor alignment etc. With one of my lenses the repair specified was something like "focus confirmation film".

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It will be interesting to see, as and when Zeiss bring out their digital Zeiss Ikon, with its longer rangefinder base, if it suffers from the same problem. I am guessing it won't.

 

Wilson

 

By now, Wilson, I am starting to feel that "as and when" should be replaced by "if ever". At this point ZI keeps repeating that the difficulties of building such a camera at the present time and in the forseeable future are insurmountable. We should give Leica credit for surmounting them, with all the bumps and glitches that go with the process. I'm sure you have been working with similar "on or beyond the cutting edge" stuff in your other field as well.

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By now, Wilson, I am starting to feel that "as and when" should be replaced by "if ever". At this point ZI keeps repeating that the difficulties of building such a camera at the present time and in the forseeable future are insurmountable. We should give Leica credit for surmounting them, with all the bumps and glitches that go with the process. I'm sure you have been working with similar "on or beyond the cutting edge" stuff in your other field as well.

 

Jaap,

 

I don't really understand the technical difficulties of this, given that the Epson RD-1 was made in the same shop as the ZI. It surely would not be a huge task to come to an agreement with Epson to use some of their concept, use the better quality frame and viewfinder of the ZI rather than the Voigtlander R2, go to Imacon or Dalsa for an improved micro-lens APS-C or -H sensor of 10-12 MP, develop the whole thing for say 6 months and there you have it. I suspect it is more a case of the will to do it rather than the technical challenge. If I were Zeiss, I would have it as a priority now. It would outsell the quite nice but semi-obsolete film ZI by I would guess, a factor of 10 or 20 to 1. They would sell lots more ZM lenses as well.

 

Wilson

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Jaap,

 

I don't really understand the technical difficulties of this, given that the Epson RD-1 was made in the same shop as the ZI. It surely would not be a huge task to come to an agreement with Epson to use some of their concept, use the better quality frame and viewfinder of the ZI rather than the Voigtlander R2, go to Imacon or Dalsa for an improved micro-lens APS-C or -H sensor of 10-12 MP, develop the whole thing for say 6 months and there you have it. I suspect it is more a case of the will to do it rather than the technical challenge. If I were Zeiss, I would have it as a priority now. It would outsell the quite nice but semi-obsolete film ZI by I would guess, a factor of 10 or 20 to 1. They would sell lots more ZM lenses as well.

 

Wilson

 

I agree fully, Wilson, but that is what ZI is saying all the time....

Copy of a ZI mail, that I lifted of RFF:

 

Dear Mr. C...,

 

thanks for your request and your interest in our products.

Within the next time, it seems not to be possible to offer a high class digital rangefinder camera that fulfills all requirements regarding sensor size, image quality and price.

 

Best Regards

 

Bertram Hönlinger

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My estimate is that Leica will have spent at least 20 man years and $20m to develop and put the M8 into production, mostly on software, tooling and production facilities. The option for Zeiss to do the same is there but whether there's an appetite to do so is another matter.

 

The M8 sets the benchmark, the R-D1 has fallen away and the ZID would have to be at least as good as the M8. Zeiss will have looked at the pain Leica went through and wiped their sweating brows with a sigh of relief.

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But may well be looking at the sales figures with envy - the eternal strife between R&D and Marketing departments....

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My estimate is that Leica will have spent at least 20 man years and $20m to develop and put the M8 into production, mostly on software, tooling and production facilities. The option for Zeiss to do the same is there but whether there's an appetite to do so is another matter.

 

The M8 sets the benchmark, the R-D1 has fallen away and the ZID would have to be at least as good as the M8. Zeiss will have looked at the pain Leica went through and wiped their sweating brows with a sigh of relief.

 

Mark,

 

Although I know Mr. Kobayashi of Cosina is a film enthusiast, he is also a very bright guy and a good businessman. He must know the writing is not just on the wall but on the floors and ceilings as well for his Voigtlander film camera range, as well as the ZI he makes. I bet he is selling more lenses for use on the M8 than for all his other products combined at the moment. If Zeiss will not come out and play with him, I would guess he will find another partner to make a digital RF, just like he did earlier with Epson. Leica have done a lot of the hard work and much of the R&D could be short cut by looking at the way Leica have done things, both right and wrong. I believe some guy even took an M8 apart just to see how it worked ;-}}

 

Wilson

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Guest tummydoc

Manufacturers such as Cosina recognise that the majority of the market for M-mount rangefinders prefer to pay a large premium for the Leica product vs another marque, therefore to gain market share their item needs to be priced at a small fraction of the Leica. The ZI cameras, priced approximately at the level of a secondhand M6, have sold poorly. The Voigtlanders sold well because they are (or were) priced below that of a "beater" M4-2 probably in need of several hundred additional to sort out. The Epson sold at it's original price only because it was the sole digital camera accepting M lenses, and was saved from going totally flat only by the M8's calamity-filled debut. Once the M8's ills were sorted (or accepted with resignation and/or rationalisation) the RD1 sales did indeed go flat. At this stage ZI would I wager have to price their M8-fighter at or less than half the M8's price. It isn't the same situation as exists between Canon and Nikon, the brand-loyal/fanaticism isn't in the same league.

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