neillaubenthal

Oops…noticed I put 7200 in the post subject…it's actually a 7100.

Hi folks…I've been running the above combination for probably 4 or 5 years now and recently I noticed that this combination (my normal walking around configuration as we're full time travelers although I have wide and long telephoto Sigma zooms as well) is hunting around the correct focus point instead of homing in and stopping…occasionally instead of hunting it goes to minimum focus distance then back to almost correct and then hunts back and forth.

I use BBF on the body and almost always have focus set to AF-C and d9 or d21…although I've tried all the other combinations and they make no difference.

The Sigma wide angle doesn't do it at all…but then it's a wide zoom so I wouldn't expect it to. The Sigma 50-500 works as it always has…although it does sometimes hunt a bit in low light…and it's always had issues with birds in flight against the sky at long focal lengths without helping it with some initial manual focus.

I've cleaned the lens, cleaned (blew out with air) the autofocus sensors under the mirror, cleaned the contacts on both lens and body and only got a little improvement…most of that came when I did the autofocus sensors.

What else can I try…I don't have any idea how to clean the autofocus sensors other than with air. I've been told that the lens needs to go back to Nikon for adjusting…but don't really understand how a mechanical adjustment would help solve the problem as it focuses fine manually.

Any other ideas or suggestions would be appreciated.

Thanks.

Bill_de Loc: US

Manual focus and see if the focus indicator in the camera works properly. If so, my experience three times over the years, it was the AF-s motor.

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jerryc41 Loc: Catskill Mts of NY

And finding a lens on ebay could be less expensive than a repair.

Recent sales -

https://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=nikon%2018-200mm&LH_Complete=1&LH_Sold=1&rt=nc&_trksid=p2045573.m1684

AGO

I also had a problem with my Nikon 18-200 and it turned out to be the VR. Try turning off VR to see if it still hunts.

camerapapi Loc: Miami, Fl.

I am using my 18-200 VR with my D7000. No issues.

Bear2 Loc: Southeast,, MI

I use my 18-200 VR ll on my 7200, and my 7000. Work great, no focus hunting except in very low light conditions.
This lens is on my 7200 all most all the time, and I alternate my 70-300 4.5-5.6 VR, with my 50 1.4 VR uon my 7000.

Duane

RF-4 Phantom Flyer Loc: Gilbert, Arizona USA

My 18-200 VR slowly started to refuse to focus in the 150 to 200 zoom range. Since I had already had it repaired once (for a bad internal ribbon connector) I ditched it and got another copy (used - local purchase.). It works fine and focuses through the entire zoom range. I really love the 18-200 lens. It is on my D7100 80% of the time. Good luck with getting yours working or replaced.

CO

I would use AF-S mode for static subjects. I really just use AF-C for motion such as birds in flight.

Check menu items a1: AF-C Priority Selection and a2: AF-S Priority Selection. They can be set for release or focus. I set mine to focus. This doesn't really have anything to do with your autofocus hunting but it will ensure that your image is in focus when you hit the shutter release.

toxdoc42

Anyone know if one can replace the focusing screen of a Nikon D3400 with one with a split screen or other focusing aids?

neillaubenthal

Thanks Bill. Went out today after we parked the RV and did a little testing…AF-C with single point selected. At low to mid zooms the hunting is much less pronounced. At 200mm and about 8 or 10 feet range I focused on the vertical edge of a white label about 2x3 inches with red printing on it on the side of our RV which is medium brown so plenty of contrast with the label which was in full sunlight…body was resting on a picnic table. Autofocus would not settle in…it did the same as before…got almost right, hunted back and forth a couple times, went to minimum focus, back to almost right, hunted a couple times, and repeat.

Shifted to manual focus and put the vertical white edge in the middle of the central focusing square…also tried with offsetting to the side a bit say 1/4 and 3/4 of the way across the square…and also tried other focusing points as well…all with same results.

Focused manually and to my eye it looks fine but getting it to settle in completely on the round dot for 'focused' was hard…with no focus ring movement I got some shifting back and forth between the left arrow, right arrow, both arrows, the dot, all 3 and various combinations.

So…it looks like it's focusing just fine manually and my guess is that slight shifting of the focus indicators in manual is due to very slight camera movement as it was being braced on a table and not completely fixed in place on a tripod.

Does that sound like it's likely the focus motor to you? If so…any idea what the repair cost by Nikon is? My guess is that with 2 way shipping it is very likely to be $250 at least although that's based on no firsthand knowledge of Nikon's repair costs. A new lens from B&H is about $650 and this is far and away my most commonly used lens…at least 80% of my shots.

Saw the recommendation on looking on eBay…and while I have nothing against them it's hard to really know the reputability of an individual seller or if a used lens is going to have the same issue…which if it is the focus motor is likely just wear due to usage for the past 6 years and somewhere between 40K and 50K shots. Might just be that the old one is wore out and needs replacing.

neillaubenthal

Good idea…but nope, VR has no effect. Tried on/off and in both normal and active…nothing different about the issue in any VR setting.

neillaubenthal

I'm a bit leery of eBay…did a quick search there and limited it to just the lens…prices for the VRII range from 40 to 489 (latter for new…but with the number of bad apples I've heard about on eBay I'm hesitant to go that way even if it saves me a bit of cash. The 489 one is cheaper than new from B&H, Amazon, or more mainstream dealers…but without knowing more about the seller pixelhub it's hard to know who's reputable and who's not…he does have 10,000 positive ratings in the last year and been on eBay since 2011…so he's likely one of the reputable ones…but ya never know.

Bill_de Loc: US

At this point I would contact Nikon and describe the issue. They should be able to give you a ballpark figure. If you send it in they will give you a detailed estimate for approval before doing any work.

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neillaubenthal

You're right…AF-S is better for static subjects but since I do a lot of mixed wildlife and landscape photos I've always found that AF-C using BBF works more quickly for me since I don't have to keep switching modes…Mr. Murphy can almost guarantee that on a walk through the woods you'll have it set to the wrong option…although if it's on AF-C for quick bird/animal shots switching over to AF-S for the landscape is easy…as long as you switch it back to C when you're done for the inevitable quick shot.

I've played with a1 and a2 and have settled this summer for having them set to release instead due to the focus hunt issues…might go back to focus when I get this issue resolved but for now I would miss too many shots due to "I don't think I'm in focus in the body". Part of the problem is that on the road it's hard to get anything fixed…not that there are any camera stores in most of the small town we travel through in the RV anyway…and by the time it goes off to Nikon who has to fix it anyway probably and comes back we've moved on. I likely won't get this fixed until after November 1 when we'll be stable for awhile…although we'll be in Denver in a couple of weeks and I am going to look there…and the other places we are in the meantime…for a store with an 18-200 in stock and see if they'll let me mount it on my body and verify that it's a lens problem and not a body problem…I think it's the lens but before either fixing or replacing it would like to verify…it's that 20 years worth Navy training.

neillaubenthal

Thanks…mine is mostly at the longer focal lengths as well so maybe it's time to replace. Of course…focus at shorter focal lengths is a lot easier for the lens to do anyway.