Focus problem

edited January 2015 Posted in » Nikon D3100 Forum
Hi there. I have had my Nikon for just over 2 years now and in the last few months the focusing has been stuffing up. I'm not sure if I maybe pressed a button or something, but it is still on auto focus and I don't think I have. The problem is that 50% chance when I go to take a picture I press down on the button to take the picture and looking through the viewfinder it suddenly focuses up and I can't press down to take a photo because it is all focused up it doesn't let me. This focusing can stay like this for minutes until I finally give up. I've tried moving it to another position then moving it back and it still does it. I took it to a camera shop and was told it was fine as it was working then, but then 5 minutes later its doing it again! It only does it 50% of the time and I haven't been able to pinpoint any pattern in scenery or lighting as to why it wont take. I'm going to London next week and I really want to find out the problem. Does anyone have any ideas what might be happening as I'm running out of ideas myself! Thank you.


  • edited January 2015
    When you say that your focusing “has been stuffing up” or “it suddenly focuses up”, I’m assuming that you’re saying that the autofocus is hunting? So it focuses back and forth and it just won’t lock onto what your active AF point is on?

    Anyway, there’s a few things you can try.

    1. Be absolutely sure that autofocus is on. Check the lens switch and your camera’s AF mode. Make sure it’s on AF-A.
    2. Is it too dark? Autofocus will struggle to lock if it’s too dark.
    3. Does the item you’re trying to focus on lack contrast? Autofocus looks for contrast to work, so the autofocus will struggle to lock on something like a plain-colored wall.
    4. Is your subject too close? Every lens has a minimal focus distance where it won’t be able to focus unless the subject is at least a certain distance away.
    4. Does this issue happen on every lens you have? If it does, then you can safely assume it’s not a lens issue.
    5. Turn off your camera. Un-mount the lens. Mount it back. Turn the camera back on. Sometimes that’s all it takes.
    6. Using a microfiber cloth and a tiny bit of isopropyl alcohol, clean the mounting contacts of your lens and camera body. Perhaps there’s just some communication issue between your camera and the lens AF motor. A simple cleaning is often all it needs.
    7. Clean your lens and/or filter if you use one. Maybe there’s some grease or dirt on it that the camera is trying to focus on.

    If after all that, you’re still having issues, then you need to bring it in for servicing.
  • edited January 2015
    One thing not mentioned above - if you are using single point auto focus, make sure the focus point is centered on your subject. It's easy to move that focus point by accident and not always to notice. Hit the "OK" button to recenter it.

  • Hi @agc - Both @ohyeahar and @bruto offered up some great suggestions. I would give their recommendations a try and see if that clears things up for you.
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