Summicron dual range back focus

[valdas]

I posted some time ago about my new purchase - I was hunting a M4 body, but happen to buy the one with Summicron DR. The price was ok (1650 EUR for the combo) and I asked the seller all important questions about the lens and the camera. It now arrived and I tested it. Camera is indeed in the very good condition and works with no issues. The DR is a bit of the problem. The seller mentioned a few dust particles when I asked about haze/fungus/cleaning marks. No fungus or cleaning marks, but there is a bit of haze visible. I will probably have to CLA, but the haze is not the only issue. It back focuses a lot. And I know it is not the camera. I tested it against my other Summicron 50mm (tabbed v4) - this one is spot on. DR is off by some 15cm if tested at 1.25m and at 3m it back focuses about 1 meter. Is this something that can also be fixed during the CLA or should I return it? In any case I plan to ask for at least a partial refund to cover the CLA.

 

[Phil_F_NM]

Either partial refund or return.
If you feel comfortable with checking on the lens, unscrew the whole optical cell from the focusing mount. Do not do this with the lens on the camera. Extend the lens by setting focus to it's closest point, then grab the whole optical unit and unscrew it. Don't use the aperture ring as part of your grip because you may break the pin or deform the aperture leaf guide plate (very unlikely but possible). Don't worry about this operation, this lens, and the V2 "Rigid Cron" were both designed so the user could unscrew the optics and put them onto a macro helical or bellows focusing device for Visoflex use. If it is stuck real bad, don't force it. If you get the optical cell off the focusing mount, you should see some numbers hand engraved somewhere in there. It will either be 16 or 19. These denote the nominal focal length of the optical cell, either 51.6mm or 51.9mm which must be matched to the focusing helicoid. Most of the V2 Rigid lenses were 51.6mm (as is every other Leica 50mm BESIDES the DR Summicron). The DR is unique in that every single one of them were calibrated with a 51.9mm nominal focal length and had serialized focusing units to match them. What may have happened is that you have a 51.6mm optical cell in a 51.9mm focusing unit. There is no real way to correct this since the optics are slightly different between the two measurements. You could shim the optical cell out a little bit but your focus would suffer farther from the film plane. It may not be noticeable as DOF and stopping down could mitigate the difference. That said, your aperture indicator would no longer be at 12 o'clock, it would sit probably closer to 10 o'clock (looking at the lens from the front mounted on the camera. This would annoy most folks to the point that they'd eventually get a new lens.
Phil Forrest

 

[valdas]

^^^^
Thanks. Hm. I tried to unscrew the whole optical cell as you advised. If I don't use the aperture ring as part of my grip - what do I use? I tried to grip the very front of the lens, but then only front elements would unscrew, not the whole optical cell. And there is no enough grip below the aperture ring...

 

[lukx]

Hmm that is a little unfortunate, as the lens block usually unscrews pretty easily. You need the correct spanners to get the front half off, at least in my experience. If the front of your lens separates before the whole block unscrews then it might be difficult for a non-professional to get any further in. You could have it checked out by a professional repair person, but it's usually better to get a good lens in the first place instead of trying to make a broken one work. Unless you get a substantial refund that is. Among vintage lenses, the DR Summicron is one of the hardest to work on.

 

[valdas]

Hmm that is a little unfortunate, as the lens block usually unscrews pretty easily. You need the correct spanners to get the front half off, at least in my experience. If the front of your lens separates before the whole block unscrews then it might be difficult for a non-professional to get any further in. You could have it checked out by a professional repair person, but it's usually better to get a good lens in the first place instead of trying to make a broken one work. Unless you get a substantial refund that is. Among vintage lenses, the DR Summicron is one of the hardest to work on.

Well, it will see a professional or it will see it's way back to where it came from... In fact, was not after this lens that much, I was buying M4 and planned to probably sell DR after playing with it. But in this condition it does not make sense. I should return it or repair it. The only issue is that I would like to keep M4 which complicates things quite a bit.

 

[Rob-F]

I'm thinking, if the focal length is .3mm shorter, that would give the lens .3mm more extension, which would make it focus closer, not further away. So that ought to lead to front focusing, I should think. No?

In other words, I think there might be some other cause.

 

[Phil_F_NM]

When I initially replied, I must have misread and thought you meant 1.5cm, not 15cm! That is something very wrong with the focusing helicoid and/or the cam on the lens. It sounds like a lot is really wrong. Return it immediately.
Phil Forrest

 

[valdas]

Yes, the back focus is huge. I already filed the return request. It's a pity, because I really liked M4 (I am not sure I will be able to negotiate the return of the lens alone).

 

[Richard G]

Return absolutely. It would be so unlikely to have anything much wrong at all with a good DR focussing given the tight tolerances required for it to work in close mode with the goggles.