Nikon D50 Autofocus stops working.

Which lens is it happening with?

It is the AF-S NIKKOR 55-200mm 1:4-5.6G ED.

Try cleaning the CPU contacts on the lens (use a cotton swab moistened with alcohol). It's possible an offending contact is "dirty", which would prevent it from establishing good electrical continuity with the camera circuits responsible for activating the AF-S motor in the lens.

If that doesn't cure the problem, or it continues to act up, I would suggest you send the lens to Nikon for an inspection and or repair before your warranty expires.

P.S. - It's usually not a good idea to post your email address in a public forum.

Hi Michael,

Well, I just thought I had cleaned the contacts. I got some 91% alcohol and swabs and started working on the contacts in the camera. To my surprise, there was some black gunk that was coming off in a pretty large quantity. The contacts went from a dull bronze to a bright copper color.

The black gunk was from a thin strip of what looked like some kind of foam close to the contacts, apparently to keep foreign objects out. A small piece had come loose, just enough to get its stick-um smeared all over the contacts when a lens was twisted on.

During the cleaning process, this piece off foam just fell off. I'm sure it was there for a legitimate purpose, but it wound up hurting more than it helped, indeed doing the exact opposite of what it was engineered to do.

I have the foam and if the camera gets dirtier without it than with it, I'll glue it back on. But for now, both lenses have come back to life -- the response time on the focusing has improved, so there was definitely some interference going on.

I appreciate the response. Most helpful. And thanks for the tip about posting safety.

Ken

"The black gunk was from a thin strip of what looked like some kind of foam close to the contacts ..."

If it is the foam indicated in the photo below, that is the mirror bumper foam. It cushions the reflex mirror when it comes up. It is very, very unusual for it to deteriorate so rapidly - usually that takes years unless it comes into contact with a solvent.

If that is indeed the case, then you should have this foam replaced as soon as possible. Glad to hear that you solved your autofocus issues.

That's it!

Apparently it is a problem, because I've now heard of several people with the same problem. I hadn't used any solvent at all and this piece of foam had came loose enough to just interfere with the lens when twisted on. The black glue that was holding it on had smeared over the contacts enough over time and use to stop the auto focus from working. The foam is very, very porous and lightweight. Whatever was used to stick it down originally doesn't seem to be very good.

I'll get it replaced. I'm just glad to know what the root of the problem was.

Ken

I used a Nikon FM for years with the all the foam removed and saw with no harm to the camera, lenses, or photos.