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01-15-2013, 12:21 AM   #1
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Join Date: Jul 2012
Posts: 29
Sigma 10-20mm 3,5 IQ - service required?

as the title shows this thread is about the Sigma 10-20mm 3.5f wide angle lense. Generally this is a lense I enjoy using very much. Some time ago though I did a shot of a nearly symetrical building using this lense, a tripod and mirror lockup (see attached image). At first I was quite happy with the result, but taking a closer look I figured that the left side of the image was way sharper than the right side. In my opinion this is visible in the magnified areas as well as when just looking at the image itself (although the windows are more comparable). I can't really say why I chose (did I choose at all?) f / 6,3, still the object should be completely in the focus plane. I didn't do any keystone correction to compensate for a poor camera placement or anything else I could think of impacting just one side of the image and its quality. All the loss of image quality on the right side appears to come from the lense only.
The question is if that is a problem sigma is obliged to repair as warranty or still a level I have to live with with a lense like this? I did ask them using this image, but they just claimed (which is nothing to complain about, I guess) that they could only figure that out if I sent the lense over. They did not answer my question if that was warranty or not.
What's your opinion? Is that OK or should I get it repaired?

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01-15-2013, 01:04 AM   #2
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Join Date: Jan 2012
Posts: 19
I've just got rid of my copy of the same lens, having never been impressed with its somewhat mushy results in the corners. In the sections of the frame you highlighted here however, I had been reasonably satisfied. F5.6 would not have been the problem, because that's pretty much the optimum aperture setting for the lens. Distortion is far greater between 10 and 12mm and that's more likely to be the root cause of an apparent lack of sharpness. I agree with you though that there should in any case be a more even performance and would suggest you compile some more evidence and return the lens for repair.
01-15-2013, 08:22 PM - 1 Like   #3

Join Date: Apr 2007
Location: Oklahoma USA
Posts: 1,503
Although I had a different model sigma, I had a somewhat similar experience with it. The example you gave was probably marginal from sigma's perspective - it may depend on the individual who examines the lens. In my case sigma returned the lens - twice - with test photos they'd taken. Basically they felt the lens was adequate. I felt even their pictures showed a very slight problem, but their edges/corners weren't my edges/corners, and if only comparing the images they sent, I'd have probably been ok with the lens. Their edges were far in from the edge of the frame - more like where you're measuring at least. And their test camera was a K100, whereas by then I had a K200, so 100% to them wasn't 100% to me. Basically we had to agree to disagree.

The "service" (USA) was fairly prompt, but you still have to consider how much you want to battle over this while losing use of your lens. Once might be worth it to try, but don't expect too much. Sending it back twice like I did would probably not be productive - it just costs you shipping and doesn't accomplish anything. I will say that "evidence" you compile isn't going to buy you much - they test the lens the way they test it, which is somewhat understandable since they can't control for such things as your sensor or mount being misaligned. Incidentally you do want to verify that the problem exists with a second body - for various reason, other lenses on the same body might not exhibit the problem, at least not to the same degree. I had a K100 and K200 at the time, and the problem was more obvious on the higher-res body with both at 100%.

What I learned from the experience was the importance of testing during the return period, because it simply may not be possible to get any issues resolved later. It absolutely is a warranty issue - but only if both parties agree. It's not like the front element fell out.

Recently I posted about returning two copies of the 55-300DA, and finally receiving a good one. My understanding is that any centering issues are compounded with wide angle lenses, but my bad 55-300s were similar in performance to the wide angle - definitely weak on one side. It may be that lenses were always this erratic in quality, but we didn't have 10+mp cameras to test with. Still, back in my darkroom days when I had an enlarger to examine the frames fairly well, I didn't feel that I had any clunker lenses among my mostly consumer-grade Takumars or Canon FDs, or even leaf-shutter Topcors.

01-17-2013, 11:23 PM   #4
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Join Date: Jul 2012
Posts: 29
Original Poster
Thanks for your thoughts. I just figured I have another image facing the same problem. If you compare the balconies you might see the difference here as well. This shot has even been performed with f8.0, which should be enough for a decent quality. Paul, I will consider your thoughts and send it to Sigma at least once. If the right part of the image turns out just as the left part, then the IQ should be OK with me. Im not too much of a architecture photographer, and with landscapes the problem doesnt get too obvious.
To what wide angle lenses did you switch when giving away the sigma?


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