28/1,9 Ultron - backfocus

[zeitgeist]

Hi,

I just got myself a 28/1,9 Ultron with an adopter ring so I can use it on my Leica M6 - I encountered some serious backfocus on the first few rolls. Is there anything I should keep an eye on when using an adopter ring?

Any input is highly appreciated. Oh, I had my M6 in for CLA a few days ago. Should be fine.

Thanks in advance,

Bernhard

 

[Kim Coxon]

What make of adapter are you using?

Kim

 

[jlw]

Make sure it's the correct thickness -- it's very common for third-party adapter rings to be slightly out of spec. (Correct thickness is 0.98-0.99mm.)

A slight difference won't affect a 50mm lens except at infinity (because the rangefinder coupling is designed for the focus travel of a 50mm lens) but an out-of-spec adapter will cause focusing errors with shorter or longer lenses.

 

[zeitgeist]

It's the original Voigtländer - 28/90 mm framelines.

Might be a stupid question: but when is the lens correctly mounted? Never used a screw-mount lens before... :/ - not sure when the lens is correctly attached (shall I rotate it as far as possible?).

 

[Xmas]

Zeit

The thread is single start, it needs to be tight enough to not un-thread in service, if the adopter is dedicated a (small) dab of nail varnish should avoid vibration effects.

Noel

 

[zeitgeist]

I just did some focus tests with a different M6 body and it also seems that the focus is off. Is this a common problem when using M39 glass with the adapter ring? Or am I having a bad copy? :/

 

[photodog]

Have a camera repairman check the alignment of the lens mount on the camera. I found out that the mount on my M2 was out a bit.

 

[zeitgeist]

Let me ask again: is the camera RF alignment off (at a given distance, for example infinity) or only the results on film. The first you can fix, the second is more difficult.

Best,

Roland.

I just had CLA so looking through the viewfinder, things are perfect. It's only a problem on film/paper.

For the lens-mount: again, I had the body in for service and they told me that they adjusted distance-meter and some other things. So I suppose that the lens-mount should be fine.

I've been to the store today and they told me to send it in to Germany and have it checked there. The guy in the store told me that I might get a new lens when they find out that there is something wrong.

 

[KJB]

Hi,

I just got myself a 28/1,9 Ultron with an adopter ring so I can use it on my Leica M6 - I encountered some serious backfocus on the first few rolls. Is there anything I should keep an eye on when using an adopter ring?

Any input is highly appreciated. Oh, I had my M6 in for CLA a few days ago. Should be fine.

Thanks in advance,

Bernhard

I had this same backfocus problem with a recent Ultron 28 purchase and returned it. I have another one on order and hope this one is a keeper.

 

[zeitgeist]

Thanks for you help but I gave the lens to a friend for doing some testshots and he had also some back-focus. Meaning, the lens is going to be in for service... I'm very pissed since I got the lens brand-new.

 

[Kim Coxon]

If the lens is faulty and new, I would go back to where I bought it and ask for a replacement. It could well be that if there is a fault in the manufacture or assembly, that a service will not cure it.

Kim

Thanks for you help but I gave the lens to a friend for doing some testshots and he had also some back-focus. Meaning, the lens is going to be in for service... I'm very pissed since I got the lens brand-new.

 

[x-ray]

Is the RF aligned at infinity ?

If yes, it shouldn't be the adapter - something wrong with the lens.

Roland.

Correct! It's certainly possible for the focusing cam to have been improperly ground or installed. I was just looking at the new LHSA magazine last night and there was a rather poor comparison of the asph 50 summilux vs the 50 millinium 1.4 Nikkor. Even though the guy concluded the lens to be virtually equal his tests were rather poorly executed. In one test of DOF the image from the Nikkor showed typical DOF distribution in front and behind the point of actual focus. The Leica asph shifted the focus noticably forward. His conclusion was there was something in the floating elements moving the focal area to improve sharpness in close focusing. The tester spoke with the designer of the asph in Germany and the fellow who designed the lens was not aware of any design feature that would do this. In my opinion it only showed the focusing cam was improperly installed or ground wrong and poor quality controll in the asph.