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I think this is really a lens issue but since it's happening with my D7100 I'll post here. My 18-200 Nikon zoom recently started hunting during autofocus. I use BBF and normally have AFS-C and d21 set. It seems to focus then either hunt back and forth slightly around the correct focus point…even for stationary subjects like tree stumps. Alternatively…sometimes instead of hunting it zooms to minimum focus distance then back to approximately correct…then either hunts around that point or goes to minimum distance.
Neither my Sigma 10-20 or Sigma 50-500 exhibit the same symptoms; although the 50-500 did until I locked the mirror up and used a can of air to blast off the autofocus sensors. Mirror is clean, and I have sensor cleaning set for both startup and shutdown. The 18-200 exhibits the same symptoms when moved to my wife's D7000…leading me to think it's the lens and not the body.
I've tried selecting AF-S, AF-A and various other focus point selection options including single but that doesn't fix the issue.
I've cleaned the front and rear lens surfaces…as well as the UV filter it's always got on it…and even tried leaving the filter off in case that was it as it is a couple years old and is showing some minor scratching on the filter outside surface…but they're small enough that I wouldn't think they're any issue. Internally…at least as well as I can tell holding the lens up to the light…I don't see anything to cause a problem.
Is this a sign that there's something wrong with the lens…or does it just need a good internal cleaning at the shop…or possibly something else? Trying to figure out where to troubleshoot next. How about needing a professional cleaning on the body to get the autofocus sensors cleaned…as I said I blew any dust out but if there's something adhering to them it might not have gotten blown off and you really can't see down into the autofocus sensor well very well. Both cameras…along with lenses and other gear…are 5-6 years old and have traveled extensively to AK and the west where it's dusty…but there isn't any indication on photos of any dust buildup that I can see.
Thanks.
Neither my Sigma 10-20 or Sigma 50-500 exhibit the same symptoms; although the 50-500 did until I locked the mirror up and used a can of air to blast off the autofocus sensors. Mirror is clean, and I have sensor cleaning set for both startup and shutdown. The 18-200 exhibits the same symptoms when moved to my wife's D7000…leading me to think it's the lens and not the body.
I've tried selecting AF-S, AF-A and various other focus point selection options including single but that doesn't fix the issue.
I've cleaned the front and rear lens surfaces…as well as the UV filter it's always got on it…and even tried leaving the filter off in case that was it as it is a couple years old and is showing some minor scratching on the filter outside surface…but they're small enough that I wouldn't think they're any issue. Internally…at least as well as I can tell holding the lens up to the light…I don't see anything to cause a problem.
Is this a sign that there's something wrong with the lens…or does it just need a good internal cleaning at the shop…or possibly something else? Trying to figure out where to troubleshoot next. How about needing a professional cleaning on the body to get the autofocus sensors cleaned…as I said I blew any dust out but if there's something adhering to them it might not have gotten blown off and you really can't see down into the autofocus sensor well very well. Both cameras…along with lenses and other gear…are 5-6 years old and have traveled extensively to AK and the west where it's dusty…but there isn't any indication on photos of any dust buildup that I can see.
Thanks.
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