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Short version

After an attempt to fix a broken Nikon 18-55 VR, the focus range has shifted. Now it focuses from very close to to maybe 30 cm beyond the lens, but not to infinity.

How can I fix this? In particular, has anyone seen any online technical e-guides about dealing with this particular problem?

Long version

My Nikon 18-55 broke recently, apparently spontaneously. The zoom ring stopped turning beyond a certain point. I foolishly put it on the camera and tried focusing, which worked to a point, but made a strange whining noise beyond that, so I didn't try further. At that point I also noticed that the front of the barrel got loose.

I concluded that it may be broken for good, and sending it in to have it fixed may cost more than buying a second hand replacement. Thus I thought that it can't hurt to try to fix it myself. I may not succeed (likely), but I can't make things worse. And at least I may find the cause of the problem, which may help me figure out why it broke in the first place. I didn't mishandle it and I can't recall it ever getting hit (but it's 8 yrs old).

After some false starts, I took off the front element based on a YouTube guide. A small plastic ring of maybe 2 mm diameter fell out. I could see where it came from: there are some spiral shaped cuts on the inner barrel which let it move back and forward as it is being turned. There are metal pins that slide in these cuts. These metal pins have plastic rings around them, which fit tightly into the spiral cut. One of the three pins had the ring fall off it.

I put the small plastic ring back, which fixed the problems with the zoom ring and fixed the loose front barrel.

But now the lens's focus range seems to have shifted. It can focus closer than before but it cannot focus to infinity (regardless of whether I use MF or AF). I don't see how I could have caused this as I didn't disassemble it completely and didn't touch (or expose) the focusing part. Maybe something shifted when I foolishly tried to use the AF right after I noticed the breakage.

Questions:

  • What could have caused the focus to shift?
  • Is there a realistic chance that I could fix this myself?
  • Are there any guides on fixing this, especially for this particular lens?

I did find a service manual for this lens, but got discouraged at the step where it says that lens alignment work will be necessary if these screws are touched.

  • When I couldn't google up anything, I thought I'd try on SE. – Szabolcs Nov 20 '16 at 16:40
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If the lens now focuses closer than before, it means when you put it back together you wound up with the front of the lens further from the camera's sensor than before. Is it possible you flipped a part with an offset meant to place the front of the lens further back? And by flipping it you would have wound up with the front of the lens further forward?

It might also be possible you didn't screw the front element group completely back into the filter ring. If the washer is also threaded (It's hard to tell from the service manual) be sure the washer is flat against the front group unit when you screw both into the filter ring together.

  • It's a good guess but I doubt it. It was pretty simple to take off the front, I just had to screw it out. There were two washers underneath. I kept them in the same position as they were. You can see the structure in this video. – Szabolcs Nov 20 '16 at 22:34
  • Well something has resulted in the front of the lens being further forward with respect to your camera's sensor. That's how you get it to focus closer. To fix it you need to figure out how to get the front of the lens further back with respect to your camera's sensor.. – Michael C Nov 20 '16 at 22:58
  • Did you screw the front element group back into the filter ring with the washer already in the lens or flat against the back of the front element group? – Michael C Nov 20 '16 at 23:25

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