Does all Sigma 120-300 OS lenses have this focus problem?

Started Oct 8, 2011 | Discussions thread
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Does all Sigma 120-300 OS lenses have this focus problem?
Oct 8, 2011

I bought a new Sigma 120-300 OS lens this week and went photographing some birds in flight. I made three trips this week with the lens and every time there were some haults with the lens af. Sometimes the lens didn't get focus on a bird and the motor just tried to do something.

I told my story on a small forum and I got several same kind of stories with their Sigma 120-300 OS lens. All of those lenses were with Nikon mount. ( actually I haven't talked anyone who doesn't have this problem and have tested this )

I found one clear way ( didn't try many different ways ) to repeat the problem over and over again.
1. focus quite close ( 3-5m )
2. then try to focus something above you further than 10m

-> AF-motor just halts and camera doesn't get any focus. Some times camera got the focus after 10s of trying.

I did a small video which shows the problem more clearly:

Now I would be really intrested to hear does anyone else have noticed this problem? Can anyone repeat the problem with their own lens? Are all problematic lenses with Nikon mount?

If this is more a "feature" than a problem which can be fixed for good, I won't be looking after Sigma lenses anymore. It's really annoying when you get bird flying over you and the lens doesn't focus.

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