Sigma 50mm focusing issue


marklj

Link Posted 20/05/2011 - 10:23
Treated myself to a Sigma 50mm f1.4. Most of the shots I've taken with it have been fairly close range portrait type shots that I've been very happy with. However, I've taken a couple of long range landscape type shots recently that are nowehere near as sharp. It appears as if it doesn't focus very well at infinity. Is that possible for a lens to focus close ok but not for longer distances?
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karma mechanic

Link Posted 20/05/2011 - 10:35
It isn't uncommon. The only way to be sure is to put the camera on a tripod and focus carefully with LiveView (if you have it) or the optical viewfinder. Use the widest aperture. Then try the autofocus, preferably by defocussing the lens first so that it has to start again - putting your hand in front of the camera and making it focus on that works. If you don't do that it will probably just use the focus setting you've just set manually.

Once you have some pictures with different focussing methods compare them closely.

Then post them here for discussion...
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fatspider

Link Posted 20/05/2011 - 10:47
I think the above reply sums it up but heres my two penneth anywyay.

I get the imprssion from the blurb on this lens that its more suited to portrait work.

From the lens description; It creates a very attractive blur, even when a small aperture is used.

Is that a clever way of saying its soft around the edges are you sure its a focus problem and not softness?
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johnriley

Link Posted 20/05/2011 - 10:58
Lenses are designed for different purposes, but generally manufacturers are pretty vague as to how they describe them. If only they would come clean as to what the properties of a design are, then we could all buy the one that suits our purpose. First time....
Best regards, John

johnwhit

Link Posted 20/05/2011 - 13:31
You don't mention the aperture in use, have you tried the lens at f/5.6 or f/8 for increased DoF, also it's probably the optimum aperture and may resolve any issues with softness at the edge of the image.

John
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marklj

Link Posted 20/05/2011 - 14:14
Tried it at all apertures and speeds and on a tripod as well. Softness at the edge isn't the issue - its the out of focus look dead centre thats the problem. Its a lovely portrait lens and thats pretty much it. With hindsight I'd have saved a bit more and gone for the 50-135 which would likely have suited me far better.
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johnriley

Link Posted 20/05/2011 - 14:21
Perhaps you could post an example image?

It doesn't sound right in that almost any modern lens, especially an expensive prime, should be able to produce sharp images as a matter of course.
Best regards, John

marklj

Link Posted 20/05/2011 - 14:40
I'll go out over the weekend John and do a couple of landscape shots with it. I've binned everything to hand that was oof.
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