Back focusing Summilux 35mm Pre asph

[Fraser]

Something is up with my 35mm Summilux pre-asph its back focusing really badly probably a good six-ten inches at ten feet, had it to local repair guy who is pretty good but he can't work out what's wrong with it and sees no way of adjusting the rangefinder cam,
Any ideas that I could maybe pass on before I send it somewhere else for repair, as he has a fast turnaround.
Thanks.

 

[peterm1]

This may be a long shot. Which camera are you using and does this happen with other lenses on that camera? Also does the rangefinder seem to align properly at infinity or is it only at closer distances?

I had a similar problem with various lenses on my Leica M8 but especially fast ones which of course have shallower DOF when shot open. The web is full of postings about the rangefinder "drifting" on this camera with use, especially at shorter focusing distances. I gather there are two adjustment points in the rangefinder unit for Leica Ms - one for infinity and one for close range adjustment. It was the latter that needed adjusting in my case. This seemed to fix it but it does seem to be drifing out once more. I do not believe Leica has acknowledged the issue at all but there are so many posts on the subject that it seems real. I think I recall Dante Stella saying that Leica M rangefinders can do this with constant lens changing but I have never had problems with my film Ms and the problem I experienced seems greater with their digital cameras. Just a thought.

I have previously posted on this site, a detailed description on how to test a camera/lens combo by setting the camera up on a tripod then using a length of wood placed on the floor in front of the tripod with a central focusing point marked marked on it and set at 3 metres distance from the plane of the sensor /film to check close focus. I also mark on the wood, specific known distances in one centimetre increments both in front of and behind a marked focusing point. By focusing on the focus point, first using the rangefinder then using the scale focus on the lens set to 3 metres (or whatever distance you have chosen for the focus point - I chose mine to match the markings on my specific lenses) I can compare results. If the lens is only back-focusing when using scale focusing then this suggests the problem is with the lens not the camera. If it is back-focusing when using the rangefinder it is more likely the camera not the lens. (You are a bit stumped it it does it with both forms of focusing but that is unlikely). If you have more than one lens it is worth doing this with each lens as that narrows down the "culprit"

This is a good way of finding out if the problem really is with that lens. Obviously this works best with a digital camera of course as you can get more or less instant feedback, film takes longer of course. It may be worth a go. It is worth doing this I found out as when I sent the camera / lens to the camera tech I was able to provide the photos taken at each test and with each lens so he could see for himself what was going on. BTW I also placed a piece of paper beside the focus point with each shot to record the lens used, the aperture used, and whether it was focused by scale or by rangefinder. That saves a lot of later questions.

 

[Fraser]

Thanks for the reply but I've got five Lenses and its only this one that will not focus so its not the camera.
Cheers.

 

[Mark C]

Did it focus right at one time? And is infinity correct? Generally, when infinity is right, the rest falls in place with older Leica lenses, assuming the rangefinder is adjusted correctly. See if the rangefinder aligns perfectly at infinity with your other lenses, then this one. Then see if the image is truly focused at infinity.

 

[peterm1]

I am certainly no expert but I have picked up a couple of pieces of info over the years - not much though.

Does anyone know if the pre asph Summilux is shimmed as with some early lenses? If it is and someone has removed a shim this is one possibility as a missing shim would have elements focusing behind where it should. Although I suspect this is unlikely.

The other idea that comes to mind is that the lens has been disassembled at some time. According to my camera guy, when they are disassembled careful note has to be made of where the threads of the helical separate from each oither. This is usually done by the technician slowly unscrewing the helical till the parts are about to come apart, then marking the observed separation point on the two barrels of the two components with a lead pencil, a marker or a light scratch on the internal components to tell him how to align them when reassembling.

If this is not done and the lens is reassembled so that its screwed back together wrongly it will not focus correctly. (This always seems odd to me as usually it does not matter how two things - say a nut and a bolt - are screwed together, but with lens helicals, that apparently is how it is!) This therefore strikes me as being more likely.

To fix it requires nothing more than patience, time and trial and error - disassembling then reassembling and testing till you have worked thru each possibility in turn. However it can be very time consuming given the need to test focus each time and then repeat the process if focus is still off. I only know this because I recently had a lens serviced and when chatting to him, my camera tech told me about the problem of not doing this correctly as I think he had recently needed to work on such a lens (not mine) that had been inexpertly taken apart. He explained this is something that many who are unfamiliar with rangefinder lenses might not realize and hence get wrong. Others here with more knowledge may be able to comment but I understand it is a possibility that may be worth exploring especially if you believe that the lens has been serviced.

EDIT: This article refers to the need to get the "the helix in the right place" by taking careful note of its position before dis assembly. Although referring to an old Jupiter lens the principle is the same. I include it only to demonstrate what I am talking about (and show I am not imagining things).🙂

http://www.pentax-manuals.com/repairs/j8service.pdf

 

[Fraser]

peterm1 I think thats whats probably wrong because the focus is so out and at all distances.

 

[maddoc]

What was the trick to get the focus fixed?

 

[Jerevan]

Send it off to a qualified repair person? 😉