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05-19-2012, 01:28 AM   #1
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Join Date: Feb 2008
Location: Tokyo, Japan
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16-50 2.8 won't focus to infinity

My heart dropped a few days ago after my K-5 with DA* 16-50 2.8 fell off a couch. When I picked up the camera I saw the lens was seemingly bent and broken at the point where the lens attaches to the body (plastic ring with the green ring and red alignment dot) and the zoom ring. I tried to push it back straight but was unable to budge the lens at all. Since the lens is 5 years old and no longer under warranty I decided to open it up and try to see if I could possibly salvage it - I honestly expected the lens was done for. I removed the metal attachment ring and saw that the plastic ring below it (which is held on to the lens by 4 screws) had 2 of the screw heads break through the plastic.Half the ring was screwed on correctly while the other half was sitting on top of 2 of the screws it was supposed to be under- this is why it looked bent and why I could not push it back in to place - the 2 screw heads keeping my from pushing the ring back in. I now wish I'd taken photos of this before I fiddled with the lens to make this explanation make sense.

I unscrewed the 2 remaining screws holding the plate in place, removed the plate and the spring loaded aperture control attached to it. The 2 screws that had gone underneath were still good so I removed them (they also had their heads somehow forced through the screw holes without completely breaking those holes - in other words I would later be able to screw that plate back in with all 4 screws actually holding the plate in place). That was it - that was the whole problem. I saw nothing else broken or bent. I had a tough time putting the rubber gasket back on, but other than that I was able to ressemble the lens with seemingly no problems. It was tough aligning the six metal electrical contacts with the holes in the metal attachment ring they fit in, but with some careful handling was able to do it. Well, when I put it back on the camera it seemed to work fine. It was night and I was indoors so I tried a few shots. All was well.

The next day I was out and about and tried a few shots and noticed a problem. I could focus on near objects without problems. As I focused on anything more than about 5 feet while at 16mm the camera would never confirm focus. It would stop at and show infinity but focus would actually be something closer to 5 feet. If I zoomed in to 50mm or even 40 or 30 and focus on a distant object I could get the camera to focus and confirm focus and would have clear images - obviously focused at infinity. I did all this at f2.8 to get a good idea of what I was dealing with. I know at such a wide open aperture any slight error in the camera's focusing can show up as out of focus, but this lens was always very accurate wide open (at least my copy - I know this particular lens has had it's QC issues).

Bottom line - the camera focuses just fine zoomed in. At 16mm and other wide angles (i haven't pinpointed where the change happens) the camera won't focus on objects any further than a few (five-ish) feet in front of it even though the focus window shows infinity. It's like either the drop or my opening and tinkering (there really wasn't much tinkering) messed up the threading/collimation/alignment of the focus system. I'm willing to send it off to get fixed but really don't know how much that would cost. I also just now learned that the price for this lens has gone way up - about 50% more than I paid for it when it first came out and more than 2x the lowest price I ever saw it for a couple of years ago. That means I won't be replacing it with a new one - self tinkering or repair shop are my only options. Does anyone have any inputs on what I can do to fix it myself? Thanks.

BTW, the camera is just fine. I tried several other lenses on it - all focused well at all zoom settings.

05-19-2012, 05:26 AM   #2
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Join Date: Dec 2007
Location: Ann Arbor - US
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Posts: 55
Same thing happened to my 50-135 after a drop. Had to send it in for repair.

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