Help! My 18-200 nikon lens won't focus to infinity!

[lostris]

Hi guys. Yesterday, while trying to capture the lunar eclipse, I discovered that my 18-200 nikon vr lens will not focus to infinity. This is new and frusterating! I have tried several different settings both manual and auto and the camera will take a picture but not focus the far distance. I have cleaned the sensors both on the camera and lens and have used a different lens with success, so I have ruled out issues with the D90. Has anyone experienced this before or know what is happening? I appreciate and thank any help in advance!
cheers,
Pam

[skunky]

Are you saying that the focus ring wont physically rotate to the point where the focus gauge shows infinity, or that the shots dont look sharp when the lens is manually set to infinity?

[ricktas]

Some lenses go past infinity..hehe! in manual, they actually turn to far, so when you turn the focus ring and hit the 'bump' the lens has gone further than the infinity point. Try easing the ring back just a fraction. If you are using autofocus, autofocus works by seeing contrast edges to lock focus, a nice bright moon doesn't really have a lot of contrast, and the lens can often not lock onto it. Try focusing on a plain blue sky with no clouds ! Manual focus is the only way in some circumstances, due to the limitations of the AF system.

[arthurking83]

Also as per Rick's reply(would be the most logical explanation) try to set the central focus point to the moon's edge and not the direct centre of the moon.

[ving]

googling this i found that it is a well known problem with this lens... I dont have a solution yet

[ving]

have a look at your front element... is it loose like this persons?

http://forums.photographyreview.com/...54&postcount=4

[lostris]

Thanks for the replies and suggestions everyone. Ving, how could I tell if the front element is loose and how would I tighten it? Rick, no blue sky today, unfortunately. I tried to focus on the grey, to no avail.
The lens/camera situation is really playing up. I cannot focus, manually or using an autofocus point, on anything far away. For instance, a picture I tried to take of mountains will not focus correctly. The camera will tell me r05 or r07 which I think means that the buffer is full. How can this be so, if I have not taken a picture for over say, 10 minutes and there are 60 or so frames available on my card? And I have to back off to about 60mm or so before I am able to fire a shot. At this focal length elements in the photo seem to be reasonably sharp (but not ideal) It also seems like the shutter is really slow, about half a second, even at extreme settings of 1/2500, F 4.8 and iso 800, where the shutter would be really quick.
Any suggestions are appreciated as this is really frustrating.

[ricktas]

Try cleaning the contacts, both on the camera body and on the lens. You may have dirty contacts.

[lostris]

Thanks Rick. I did try doing that yesterday, but will do it again, possibly properly this time! Hopefully it works.

[skunky]

Dont be confused by mistaking the r04 and r07 errors as buffer warnings. When no shots are in the buffer, these errors relate to problems with the AF. The r04 error in particular relates to the inability to gain focus.vAs Rick said, you'll have a great deal of trouble focusing on the moon or any subject low levels of contrast.

AF modules commonly need a lens with an aperture of less than or equal to f5.6 in order to capture enough light to focus correctly.vThe fact that you're able to automatically focus when you set the focal length to 60mm is a pretty good sign that your AF module isnt getting enough light to focus properly on fairly low contrast objects at a distance. You're using a variable aperture lens, so as the focal length increases, so does the aperture which allows less light through as you creep toward the 200mm limit.

Theres likely nothing wrong with the lens or body (aside from needing a faster lens for what you're trying to do ), but more so with the subjects that you're trying to capture. For future moon shoots, you might want to try and set the lens to manual focus mode and the focal distance to infinity by hand.

[lostris]

Thanks for the input guys. Unfortunately, after many attempts at cleaning the contacts both on the lens and camera, the problem persists. I might try taking it down to a camera shop in town and have them look at it. Does anyone have any advice as to where they send lenses for maintenance/repair etc?
cheers

[skunky]

Did you end up trying to focus on a subject with high contrast at 200mm in order to verify as to whether it's actually a problem with the lens or if it's related to a lack of contrast in the subjects that you've been trying to shoot?

I'd recommend testing this perhaps the corner of a wall or a roof at what would be the lenses equiv focus of infinitely. So pick a target a good hundred meters away or more.

[arthurking83]

Before you do go down the send it in for a checkup route, I'd be inclined to do a few things as skunky's advice suggests.

Focus on a few objects like trees, or buildings at some distance away.

is this issue only at 200mm or at any focal length?
How are you focusing? What focus mode(AF-S, AF-C, AF-A)? What camera body?
is it only a problem for AF, or is the problem no focus at all, even manually, at infinity?
if it's af only, do you have a UV/protective filter fitted to the lens? if so, remove it!
do you have any access to another body at all?.. friends, family, AP member next door.... ?

etc, etc.

I'd be inclined to use any repair/service department only as a last resort, after trying every possible avenue either myself or with the help of others, either online or in person.

[fillum]

Just to add to skunky and AK's posts, when you try to focus manually at something in the far distance (ie at infinity) does the image appear in focus in the viewfinder?


Cheers.

[lostris]

Good news! I finally got my lens fixed! It turned out to be a problem with the front element. Ving you were right! Yeah! Back to taking pictures again! Thanks everyone for your help and input.