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07-22-2012, 03:29 PM   #1
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Lens issue - Dirty contacts?.....

Sorry - As I'm sure this has probably been answered in other posts before, but I'm on vacation and only going to have internet access tonight, so I was hoping for a quick confirmation/answer.

My DA*50-135 just lost its ability to auto focus a few hours ago. It was working fine, and then the last time I mounted it I noticed the AF button wasn't working. Then I noticed that "MF" was showing in the viewfinder. I tested the lens on my other body, with the same result - and I test the body with another lens that AF's just fine, so I'm assuming/hoping that the contacts may just be dirty?

The only reason I'm questioning that it may not be the contacts is because with all the lens switching I've been doing the last few days the rear lens cap from my Sigma 10-20 has been going ont the 50-135 a lot, and as you may know that cover is sort of "finicky". It's tought to get on, and you really have to work to get it on square, so I just want to be sure that the AF issue is related to the pins on the back of the lens? (I don't think I've messed anything up with the pins, but just wanted to be sure that wasn't an option - as I think it's the contacts that control the AF.

So - if it IS probably just dirty contacts on the lens - what's the best way to clean them? I seem to remember reading about using a pencil eraser, but I want to be sure before I attempt - in case I'm wrong and all the little rubber "flakes" mess something else up.

Any help/info would be appreciated - especially while I still have internet acces for the next 14 hours or so.
If not, no big deal, as I'll just MF when I use it, and find the answer when I get home from vacation.

Thhanks in advance for any help,


07-22-2012, 05:23 PM   #2
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Check the pins carefully to be sure they are are still in the proper position. Compare to another lens.

However, the AF is controlled by the powerzoom contacts, that's the two down inside the camera mount, not the ones out on the rim of the mount.

Cleaning is best attempted (in the field) by buffing gently with a micro-fibre cloth. I would not use the pencil eraser thing, it might work but if your contacts are that corroded you need more help anyway and you can get flakes in the body.

However, this sounds more like SDM failure than dirty contacts. In which case there is nothing to do but send it in for repair. By all means check all the pins and clean everything but it does not sound good to me.

I am sure you checked but make sure both the AF switch on camera and on lens are in the AF position. I would move them back & forth to be sure.

Wish I could do more but I think you are SOL.
07-22-2012, 05:26 PM   #3
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I just used a swab with a little 91% rubbing alcohol on it last time. It was a rented lens that had a sporadic AF until i wiped the contacts and then it was fine. No doubt there are better cleaning solutions for electrical contacts but I bet just a dry paper towel would work also.
07-23-2012, 10:09 AM   #4
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It almost looks like you hit the AF / MF body switch

07-24-2012, 06:30 PM   #5
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QuoteOriginally posted by Lowell Goudge Quote
It almost looks like you hit the AF / MF body switch
Almost. I think it may have been the switch on the lens. I had tried the switch on the body a few times to no avail. After reading jatrax's post (thanks jatrax), I switched the switch on the lens off and on (I.E. to MF & then back to AF) - and then it worked. The switch LOOKED like it was still on AF, but it must have been ever so slightly off.
Thanks to all for the comments/ideas/help.....


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