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12-07-2017, 08:07 AM   #1
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Sigma 10-20 f4-5.6 repair question

I recently bought a used 10-20 f4-5.6 that, in my opinion, had a left side softness issue. After some Googling this appeared to be fairly common and usually caused by a decentered element. I sent the lens back to Sigma, who two days later has identified the fix as "need to adjust AF data". This makes no sense to me, because this isn't an auto focus issue. The left side is soft regardless of auto or manual focus and the auto focus works just fine... on the other 2/3 of the image that is actually sharp.

Obviously I've voiced these concerns to Sigma and am waiting to hear back, but in the mean time does anyone else have experience with Sigma service and possibly even this particular issue (I know this lens and this issue are quite common)? I'm not going to pay Sigma $125 to do something I can do myself with micro focus adjustment.

12-07-2017, 09:05 AM - 1 Like   #2
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To be honest, it has been my experience that it usally doesn't worth it to send back cheap standard consumer grade lenses for repair outside warranty coverage, no matter if it's Sigma or any other manufacturer. More often than not, the repair will cost almost as much as buying another lens. And that's even supposing the repair solve the problem in the first place, which is often not the case.

More than probably you will get back a lens that is "in specs" but still having some problem since the tolerances often seem quite large with consumer lenses, particularly with third party manufacturers.
12-07-2017, 06:17 PM   #3
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I have had this exact problem with this exact lens. I sent it to Sigma twice but we couldn't agree on what constituted adequate performance. Notably, Sigma's idea of "edge" wasn't close to mine (it was considerably in from the edge of the APS frame), and their only body was 6mp while mine was 10mp, and this is one place where mp does make a difference in the degree to which resolution issues show up.

A second copy was much better and I still use it, but even it seems to be temperamental: sometimes I do get a blurry edge/corner (not always the same ones) in real life, but the bottom line was that I did a test by moving the body on a tripod so a traffic sign about 50ft away was placed in each corner of the frame, with AF and SR off, using manual exposure and different focal length settings) with both copies. With the second copy all the corners were very, very close. In real life sometimes there are other issues - filters, subject distances, etc. - so it's a much less controlled situation. Honestly something still might be wrong but I know it's not something I'm willing to work that hard to find. At some point you can wear your camera body out shooting resolution tests at every focal length, focus distance, etc. (I think I almost did between these two lenses and all my copies of the 55-300.) The traffic sign tests were night and day different between the two copies of the lens, and consistent and repeatable. The first copy was just consistently and obviously bad on one side - there was nothing mysterious about it.

In general I don't think you can count on any manufacturer to fix decentering. When I got a Pentax 60-250, AF was off by +10 - but I kept it vs. sending it back because it wasn't decentered. I figured the odds of getting another non-decentered copy weren't good, and Pentax could fix the AF. And they did. I'm not convinced they could have fixed decentering, because nobody has ever explained to me exactly how that's done.
12-07-2017, 06:18 PM   #4
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QuoteOriginally posted by CarlJF Quote
To be honest, it has been my experience that it usally doesn't worth it to send back cheap standard consumer grade lenses for repair outside warranty coverage, no matter if it's Sigma or any other manufacturer. More often than not, the repair will cost almost as much as buying another lens. And that's even supposing the repair solve the problem in the first place, which is often not the case.

More than probably you will get back a lens that is "in specs" but still having some problem since the tolerances often seem quite large with consumer lenses, particularly with third party manufacturers.
I don't think I would characterize the Sigma EX line as cheap consumer-grade lenses, although I agree with your conclusion. I'd consider it more mid-range.


Last edited by tibbitts; 12-07-2017 at 06:25 PM.
6 Days Ago   #5
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QuoteOriginally posted by tibbitts Quote
I don't think I would characterize the Sigma EX line as cheap consumer-grade lenses, although I agree with your conclusion. I'd consider it more mid-range.
By "cheap", I was only refering to its actual price and not its overall quality. This lens can be had today for about 300$ or even less if you're lucky. Which is cheap for a UWA zoom, or even relative to lenses in general...

BTW, my experience with this lens and Sigma has been similar to yours. I was not satisifed with the performance of the lens and send it to Sigma for verification. They've done nothing since the lens was "within specifications". Maybe it was a bad copy, but I jus got rid of it after that.

Last edited by CarlJF; 6 Days Ago at 07:48 AM.
6 Days Ago   #6
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QuoteOriginally posted by tibbitts Quote
At some point you can wear your camera body out shooting resolution tests at every focal length, focus distance, etc. (I think I almost did between these two lenses and all my copies of the 55-300.) The traffic sign tests were night and day different between the two copies of the lens, and consistent and repeatable. The first copy was just consistently and obviously bad on one side - there was nothing mysterious about it.
I'm with you on that 100%. I'm not a pixel peeper. Like a moron I deleted my example shots, so can't share anything to show the issue, but this isn't a pixel peeping issue. This is a "wtf is wrong with that lens" issue that is glaringly obvious at any view size larger than an Instagram photo on a cell phone. It isn't just totally blurry, but the rectilinear correction seems grossly off on the left side, hugely pulling down and distorting objects on the left side about twice as much as on the right side. Both these issues improve slightly after F7 and above 12mm, but are no where near satisfactory and, in fact, given that these settings make the right side look so nice, the left side issues (while better than wide open at 10mm) stand out even more.

As for the decentering. I have seen numerous threads on other camera boards where owners claimed Sigma did fix their decentered element issue (not sure how), but in those cases Sigma correctly identified the issue as decentering rather than this "needs AF data adjusted".


QuoteQuote:
By "cheap", I was only refering to its actual price and not its overall quality. This lens can be had today for about 300$ or even less if you're lucky. Which is cheap for a UWA zoom, or even relative to lenses in general...
I've never seen the f4-5.6 version of this lens new for less than $480. The consensus seems to be that the f3.5 is inferior and that one goes for as low as $260. I bought this f4-5.6 one used for $165. If I can pay Sigma $125 to get it working properly I think that's well worth it. What I don't want to do is double down on a poorly constructed copy if their "repair" isn't going to do anything to help the issue.
6 Days Ago   #7
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QuoteOriginally posted by AyeYo Quote
I'm with you on that 100%. I'm not a pixel peeper. Like a moron I deleted my example shots, so can't share anything to show the issue, but this isn't a pixel peeping issue. This is a "wtf is wrong with that lens" issue that is glaringly obvious at any view size larger than an Instagram photo on a cell phone. It isn't just totally blurry, but the rectilinear correction seems grossly off on the left side, hugely pulling down and distorting objects on the left side about twice as much as on the right side. Both these issues improve slightly after F7 and above 12mm, but are no where near satisfactory and, in fact, given that these settings make the right side look so nice, the left side issues (while better than wide open at 10mm) stand out even more.

As for the decentering. I have seen numerous threads on other camera boards where owners claimed Sigma did fix their decentered element issue (not sure how), but in those cases Sigma correctly identified the issue as decentering rather than this "needs AF data adjusted".




I've never seen the f4-5.6 version of this lens new for less than $480. The consensus seems to be that the f3.5 is inferior and that one goes for as low as $260. I bought this f4-5.6 one used for $165. If I can pay Sigma $125 to get it working properly I think that's well worth it. What I don't want to do is double down on a poorly constructed copy if their "repair" isn't going to do anything to help the issue.
My experience with the lens was that even though I could easily detect the decentering on two different bodies, I couldn't convince Sigma that it was sufficiently out of spec to do anything about it. But I'm not convinced Sigma will fix decentering, even if they can, for $125. I can believe they would charge that for cleaning and adjusting the AF. I sent mine in under warranty and even then it cost me $25 or so for the two shipments. I have read of people having the decentering fixed but in at least some of the cases I believe the lens was sent to Japan, and maybe that just meant most of the components of the lens were replaced. I just don't think it's worth the financial risk and time and effort for a low probability of success.
3 Days Ago   #8
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QuoteOriginally posted by tibbitts Quote
My experience with the lens was that even though I could easily detect the decentering on two different bodies, I couldn't convince Sigma that it was sufficiently out of spec to do anything about it. But I'm not convinced Sigma will fix decentering, even if they can, for $125. I can believe they would charge that for cleaning and adjusting the AF. I sent mine in under warranty and even then it cost me $25 or so for the two shipments. I have read of people having the decentering fixed but in at least some of the cases I believe the lens was sent to Japan, and maybe that just meant most of the components of the lens were replaced. I just don't think it's worth the financial risk and time and effort for a low probability of success.
So they emailed me back and clarified what they meant and it sounds similar to what you just said. It's $100 (plus the $25 return ship, which i absurd, I sent it USPS priority to them for half that) for them to test and calibrate the lens. If there's a deeper issue they'll "try to fix it for the original price". If they can't, they'll send a new quote. If I reject the new quote due to excessive cost, they'll refund me the original $100 as well.

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