sigma 50mm focus and sharpness

T

the jam

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I have recently purchased a sigma 1.4 50mm lens to go with my Nikon D5000.

The lens is great but the autofocus is quite clunky and the sharpness of the pictures is not as good as I would have hoped ...am I expecting too much?
 
Are you using it right? Is the sharpness problem when you use it at f1.4 and other large apertures?
 
I probably have been shooting mostly with widest aperture. Will try taking it back a bit and also do a couple of tests with a tripod ...thanks
 
the jam said:
I probably have been shooting mostly with widest aperture. Will try taking it back a bit and also do a couple of tests with a tripod ...thanks
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Also be careful when you do shoot at those wide apertures, the depth of field will be so small that any movement on your or the subjects part will throw it out of focus. I had the same problem when I first got my siggy 30mm f1.4.
 
It should in theory sharpen up at f/2.0 and become seriously sharp at f/2.8 (well that's on crop cameras, FF corners are quite poor). If it doesn't there is something wrong (technique, body or lens).
 
Should still be usable at 1.4 though. I would be concerned if it wasn't properly sharp by f2 as well, my nifty fifty certainly is by 2.8!
 
It could be that it is very slightly out of alignment for focus, mine (on a canon system) is OK on my bodies where I can do micro AF adjustment, but if I use it on one that doesn't have this the results are not great. I'm going to be sending mine in to Sigma with one of the spare bodies so they can get it spot on.

Although, it could but just that you are moving a little in your case. Go for the tripod test, good light, well defined subject and centre point only focus.
 
The lens is 99.9% likely to be ok (within manufacturing tolerances) and its just the dof. Theoretically you should get all your very fast lenses calibrated to your camera body if you want super accurate focusing.
 
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