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PostPosted: Mon Oct 03, 2011 12:49 pm 
Probably going to buy a Sigma 30mm f1.4 lens in a bit. There are some reviews describing some focusing short. What's the best way to check the one I'm looking at doesn't?

Ian


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PostPosted: Mon Oct 03, 2011 1:18 pm 
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Location: Norway
My suggestion is: Put the camera down on some surface with a fixed distance to some object. Use manual focus in live view to get the center of the frame in perfect focus. Then exit live view and half-press the shutter to focus on the same spot with the traditional phase-change system. If the focusing distance window on the lens changes, the lens has front- or back focus

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PostPosted: Wed Oct 12, 2011 1:48 pm 
don't just AF on the center,because the middle AF point is cross-type & that might influence the overall AF perfomance & precision of that lens. always try many focusing scenarios.
A Tamron 17-50mm that I tested failed completly (well it had serious front focusing issues),but only after I used all AF points,the middle AF point was much more accurate then the others. Focusing with the non-cross type points resulted in some looong hunting. (outdoors!)


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PostPosted: Wed Oct 12, 2011 4:30 pm 
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Try micro digital in Mall of the Emirates (first floor, above French Connection)

They sometimes have a selection of certain Sigma lenses so you may be able to try two copies. They'll give you a 10-15% off 'best price'

Normally the light isnt great in the store, but try close focussing on an angled advert/point of sale sign at a particular letter wide open or close to it.


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PostPosted: Wed Oct 12, 2011 6:58 pm 
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Good point on the cross-type sensor, Razvan

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