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08-01-2008, 07:44 PM   #1
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sigma 17-70mm

I guess this is for those who have this lens. I just got it and did a quick test and I noticed that the corner sharpness at 17mm is pretty bad wide open. Is this typical of yours? It didn't really get better when I stopped down. Just wondering if I got a bad copy. Thanks

08-01-2008, 08:14 PM   #2
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you should post your sample. 'pretty bad' is a relative term
08-01-2008, 08:39 PM   #3
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Ok here's my quick test. The first is the orignal image and the rest are the corners. The first 2 crops seem the worst. They are the top 2 corners of the image while the last 2 are the bottom corners. Let me know what you think please. I have a feeling I might just be trippin over nothing
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08-01-2008, 08:51 PM   #4
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the test shot is inconclusive. you should give your test shot adequate chance: use ISO 100, make sure the focus is dead-on. turn on flash or do the test with plenty of light. otherwise you're taxing the whole system and the rest of us probably would be just guessing...

08-01-2008, 10:22 PM   #5
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QuoteOriginally posted by furby Quote
I guess this is for those who have this lens. I just got it and did a quick test and I noticed that the corner sharpness at 17mm is pretty bad wide open. Is this typical of yours? It didn't really get better when I stopped down. Just wondering if I got a bad copy. Thanks
I have sent my copy immediately to Ronkonkoma, NY (Sigma Service Center) - I was completely expecting such or similar defect... Center was always good - but the left side was consistently clearly different from the right side... tested on brick walls and newspapers (from 17 to 70 and from f2.8...f4.5 to f8.0).

PS: and I did test on both *istDL and K10D so that Sigma will not escape by blaming anything
on specific camera.
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