Sigma lens autofocus problem bit strange

M

Madbull

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Chris Douglass
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Hi all
I’m Chris, I’ve been into photography for years and use a canon 5dmkii. My old faithful lens is a sigma 24-70mm dg and I love it to bits. On my last photo shoot though it started messing around. With the camera in landscape the focus is fine but turn it on it’s side (shutter button in the air) it tries to focus but can’t decide when to stop. Back to landscape not issues and angels all the way up to 90degrees fine just the last 5/10 degrees. I have tried it on different bodies with the same results and different lens work fine on my 5d. I thought it might be the contacts moving away from the camera so I would need a new ring mount. Any ideas?
 
Thanks Mike yep checked them with a #00 screwdriver. I wanted to find out how easy it would be so borrowed the screwdriver. Lens seamed to work for a couple of seconds fine and I though I had sorted it but then went back to the same problem.
 
Check that the contact between the lens and body are clean and not worn/corroded?
 
Could it be the focus point and horizontal / vertical alignment?
IE If you've selected a horizontal sensitive point, then when you rotate the camera this is now aligned to be vertical sensitive - for some points on a subject this can stop the camera achieving AF as it no longer has anything to lock onto.
 
Hi Bristilian
I have attached photos of first the problem lens and then one I don’t use as much what do you think?
 

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@Madbull - from those images it is hard to say. The one on the right looks to be more heavily contaminated or marked than the other.

It was really only a suggestion as I have had similar problems in the past which were cured by a good clean of the lens and body electrical contacts.
 
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