[timo]

If the camera tried to turn the lens even if it hits infinity, the lens is unable to focus at infinity. To adjust the lens for this issue, remove the retaining ring from the front using a piece of thick rubber, then the 3 screws and the filter ring. 3 tiny screws should expose and they are responsible for the focus adjustment. Loose them slightly (don't extract them), adjust the focus, then tighten. Threadlock is needed btw. You will need a #00 screwdriver for the job (or JIS 1.4 or 1.7mm). Good luck.

Ah - that is what I thought the process might be, in general terms. That said, I have not intention of trying to do it myself. But thanks for the info.

[timo]

OP, you mentioned that you had sent the lens to be serviced.
However a proper service also means having the lens collimated to ensure infinity focus. Unfortunately not all repair shops may have an optical collimator on hand. That is why opening up any lens runs the risk of such issues unless one has the correct tools. This is such a common problem because a lot of people think "opening up a lens, well there's nothing to it."

Denis I agree that there is a major chance of just making matters worse, let alone losing screws as they roll under the desk etc etc ... I'm not going to try DIY in this case.

[timo]

Just to say that I have done another quick and dirty test in the street today - set manually to infinity it's actually focusing to no more than 20-30 metres: easy to spot with the lens wide open.

So it's clear what the problem is - have to take it back to the guy who charged me money to service the lens and get him to fix it.

[timo]

Quick update - after one professional repairer failed twice to fix it (and charged me money for failing), I found a local amateur who knew what do do. It took him about 20 minutes to discover how to adjust the focusing ring and the lens now works as it should. wlachan's advice was basically correct - in fact the process sounded easier than with a manual lens as access to the adjustment screws only involved undoing other screws, rather than rotating the front ring with the aid of rubber gloves or a rubber implement. Optical performance now seems about the same as my M1.7, not surprisingly, although sharpness wide open is affected by the slightest AF error. It doesn't always get it quite right.

Anyway I'm happy that the lens is now fully usable, instead of just taking up space in my dry cabinet. Happy ending.

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Last edited by timo; 11-24-2010 at 04:23 PM.