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10-05-2011, 07:26 PM   #1
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Sigma Zoom Focus Issues

Autofocus with two of my Sigma lenses, the 70-200/f.5 EX APO DG Macro HSM II and 100-300/4 EX APO DG seems to get "stuck" intermittently--just will not focus on the subject. I can get it working again by turning the camera off & on and focusing at a different distance. This only happens with these lenses--both on the K-5 and K20D. They're otherwise very good lenses but this quirk can be pretty irritating when I'm shooting sports and I'd find it extremely so if I were a pro.

Has anyone else encountered this?

I don't mean this to be a Sigma-bashing thread, btw: I have a lot of respect for Sigma lenses.

10-05-2011, 07:48 PM   #2
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I have not encountered this using 70-200 HSM II on K-5 or K-x.

Contacts are clean?

On the 70-200 did you try flicking the MF/AF switch a few times to see if ift is making a good connection?

If the 100-300 is screw drive it could be a body issue.

Do you notice that the F-- indication comes on when this happens? That is usually a dirty contact problem, as the body loses communication with the lens.
10-06-2011, 04:18 AM   #3
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Thanks for the response, Larry. As I say, it seems only to happen with these lenses but regardless of body. I guess I do need to try cleaning the contacts. Thanks.
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