My Nikon 18-200 vr1 is starting to develop a problem. Zoom at 200mm will not lock focus and have to reduce zoom to 150mm or less before focus locks in. Any idea what is the problem and is it economical to have it repaired. Works the same on 2 cameras so it is the lens. Zoom at 200mm on close subjects is OK but not for distance even short distance
Back in my DX days, I was a heavy 18-200 user (first version). As others have pointed out, f/5.6 is not really very wide open, and mine also did have problems locking AF beyond 150mm, with some hunting.
But it was a consistent "non-problem" from the start: it did that as soon as I was not in bright daylight, and it is not a problem that "developped" over time. Maybe you're starting to shoot in the more interesting lights of early morning/late afternoon? That could be an explanation. Usually, as you note, closer objects are better illuminated and more contrasted, making the job of the AF really much easier than on more distant ones - and zooming back is the only solution, in order to regain a more friendly f-stop that will allow more light to reach the AF sensors.
A simple test/remedy, also, is to try with the center sensor: on most cameras, it will be a cross-type one, more sensitive than the linear ones in the periphery: on the D300 I owned, the three center columns of AF points were cross-type sensors, if I am not mistaken, and thus less prone to hunting in not-so-good lighting conditions.
If it can soothe your "pain", my 28-300 (yes, I like those "do-it-all lenses"!) does also do that in the same conditions on my D700. Using a faster lens such as the 80-200/2.8 or the 85/1.8 is also a remedy: since the lenses are wide open when composing the image and focusing, more light reaches the sensors and AF is really quicker! Calculating the figures, at 200 and f/5.6, the AF sensors get 4 times less light than at 200 and f/2.8, since the amount of light entering the lens doubles with every full f-stop: f/2.8 is twice as luminous as f/4, which in turn is twice as luminous as f/5.6.
Hope this helps!
Olivier Rychner __________________________________________ Jetez un oeil à ma galerie if you feel like it! And it's a bit void as of now, but I also have a Nikonians blog
Auta i lomë! And my Nikon's only awaiting daylight...
I see this all the time with moms trying to focus in dark gymnasiums with their 18-200's on their kids playing basketball. The lens at full 200mm needs way more light to manage that feat than most assume. They are constantly coming up to me asking why they cannot get their lens to focus. I generally take them outside into ambient light of day and tell them to "now try it". They are astonished when all goes well. They simply do not yet understand the concept of zooming and reduction in light transmission.
Strange I did not notice this before since lens is 4 year old. I was sure something has gone wrong. Now I am not sure. Focusing is problem only when trying to focus at distant trees, hills, roofs with some haze. In less distant but good contrast objects focus is instant. Thank you for your halp.
If it is happening in good light with the centre sensor then something could be wrong inside. The lens needs a high contrast AF target at full extension as others have said. Has the lens been dropped or taken a knock?
My camera with 18-200VR was blown over while mounted on a tripod a few years ago. The lens zooming and focus mechanism was damaged. I could focus and zoom manually but the mechanism was too stiff for the AF-S motor to move it. I sent it in for repairs and they replaced the zooming mechanism. The lens has worked OK since then and the cost of repair was about 1/3 the price of a new lens
I just did Total Solar Eclipse at 200mm using auto focus single focus point and it worked well with solar filter and without during totality. I was just trying recently to focus on distant trees and could not get the focus. When trees are nearer and less effected by distance haze I have instant focus. I did not notice this before but I can live with it.
I had the oportunity of testing another D7000 and 18-200 VR2 lens. Conclusion was VR2 is slightly sharper at every focal distance. Focus is instant and accurate. At 200 mm focus is good. My problem lens does not focus distant at 200 mm. If focusing manual at end of turn still can not get focus indicating green dot. With VR2 lens focus ring can be turned past green dot. Using both cameras to test lenses result is 18-200 vr1 has a problem at long end but quality of image is also not as good as VR2 lens but acceptable. I am now considering to get 70-300mm lens.
Happy to say my lens is fixed. I did search online and in flickr discussion blog suggestion was given to check if front element is loose. This can get loose when using filters. Found it loose full turn. Now focus is instant and I expect image quality will also improve.
After testing my lens all is well. Pictures are sharp and focus is instant. No one has mentioned the posibility of this being the problem. Ether everyone knows it or no one knows it, In any case someone will sometime come across this problem again. It is also good idea to check front element ring for tightness as part of lens maintenance.
I have a lens with the same issue. The zoom is a little stiff now and the focus isn't that great.
I tried the front element fix but that wasn't the issue.
Is it worth it to send it in to get fixed? I purchased a new 18-300MM Nikon lens since it has started acting up. Am I better off fixing, or just trying to sell it for a couple hundred bucks? Small scratch on the glass behind the first element. Otherwise it's in excellent condition.