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Old 1st of January 2008 (Tue)   #1
Zwiz
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Default Faulty Sigma 10-20mm?

Hello,

I've had the Sigma 10-20mm for a few months now. Some of the images are incredibly sharp but sometimes, the left side is really bad. It's not easy to pinpoint the problem since it is intermittent. It will rarely show at 10mm or when the image is oriented vertically! But from 12mm to 20mm, I would say 1 image out of 3 has the left side out of focus.

Here an image here that demonstrate the problem.
Please, tell me what you think!

Sigma 10-20mm at 12mm, f/8, 1/400sec, ISO 200, on tripod.
Full image (no crop, resize 33%):


Cropped image (100%): looking at the streets name, you can see the exact point where the lens begins to show focus problem:
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Old 1st of January 2008 (Tue)   #2
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Default Re: Faulty Sigma 10-20mm?

thats really weird, I think your lens is messed up
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Old 1st of January 2008 (Tue)   #3
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Default Re: Faulty Sigma 10-20mm?

I would call Sigma and send that in. It appears a lens is off axis just a bit inside.

Here is a thought, there aren't any smudges on the back end of the lens (side that connects to the body), are there?. The closer a smudge or any dust/dirt to the sensor, the more impact it will have on the photos.
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Old 2nd of January 2008 (Wed)   #4
Tee Why
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Default Re: Faulty Sigma 10-20mm?

Looks like the focus is on the ladder on the right.
Try some controlled testing. It is was due to a lens defect, I'd expect to see it in all the shots so I'd suspect user error over lens defect.
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Old 2nd of January 2008 (Wed)   #5
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Default Re: Faulty Sigma 10-20mm?

Quote:
Originally Posted by Tee Why View Post
Looks like the focus is on the ladder on the right.
Try some controlled testing. It is was due to a lens defect, I'd expect to see it in all the shots so I'd suspect user error over lens defect.

i concur with the above.

do you have more photos with the lens?
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Old 2nd of January 2008 (Wed)   #6
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Default Re: Faulty Sigma 10-20mm?

This appears to me to be a decentered element or two. As they move this will change the way the light path is transfered from one element to the next. Depending upon how zoomed and where the focus is the effect will vary. Just a guess...
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Old 2nd of January 2008 (Wed)   #7
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Default Re: Faulty Sigma 10-20mm?

I had a decentered element in a sigma 10-20 before; I got it replaced with a slightly less center-sharp lens, but one with no decentering issues.
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Old 2nd of January 2008 (Wed)   #8
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Default Re: Faulty Sigma 10-20mm?

Thx for the answers!

So, it could be a decentered element... Ok, I'm getting my screwdriver and my ruler right away and I'm going to do do a job on this lens. More seriously, this lens is going to Sigma. "Form", did Sigma replace or repaired your lens?

Here another one, again at f/8 on tripod. Note: this is a test image, nothing artistic about it!

Full, resized to 33%


Crop 100% Left side


Crop 100% right side
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Old 2nd of January 2008 (Wed)   #9
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Default Re: Faulty Sigma 10-20mm?

I think this was/is a common problem with this lens. I'd be sending it in for repair.
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Old 2nd of January 2008 (Wed)   #10
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Default Re: Faulty Sigma 10-20mm?

Neither; Sigma accused me of getting a grey market lens (serial number discrepancy), and said "send it in and we MIGHT consider repairing it under warranty," but the original reseller was willing to replace it.

As far as I understand, this is not necessarily the standard treatment from Sigma, but it still soured me towards them.
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Old 2nd of January 2008 (Wed)   #11
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Default Re: Faulty Sigma 10-20mm?

Quote:
Originally Posted by form View Post
Neither; Sigma accused me of getting a grey market lens (serial number discrepancy), and said "send it in and we MIGHT consider repairing it under warranty," but the original reseller was willing to replace it.

As far as I understand, this is not necessarily the standard treatment from Sigma, but it still soured me towards them.
Sigma USA won't repair grey market lenses as they are not responsible for them. The greys also come with a 1 year warranty from Sigma Japan (requiring sending the lens to Japan), while the Sigma USA EX lenses come with 4 year warranties for repair in the USA.
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Old 2nd of January 2008 (Wed)   #12
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Default Re: Faulty Sigma 10-20mm?

The seller was verified and genuine, and it was NOT marketed as grey market. If it was a grey market lens, then the head of the company lied to me directly (I spoke with him).
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Old 2nd of January 2008 (Wed)   #13
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Default Re: Faulty Sigma 10-20mm?

That's a bummer. I always buy my EX lenses from B&H since they only get theirs from Sigma USA. That way, all I need is the receipt that shows B&H's logo to verify it's legit. I get my non-EX Sigmas from Sigma4Less, which are usually grey market and only have the 1 year warranty anyway.

I hope you got your problem resolved satisfactorily.
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Old 2nd of January 2008 (Wed)   #14
Tee Why
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Default Re: Faulty Sigma 10-20mm?

The image looks slightly tilted down and not perfectly aligned, but to me, it does look more like misaligned lens/optics.

I'd send it into Sigma.
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Old 2nd of January 2008 (Wed)   #15
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Default Re: Faulty Sigma 10-20mm?

I had four of these lenses that looked exactly like yours. All were decentered, and three were Amazon RMA replacements. The last, I sent to Sigma. It came back significantly worse than how I sent it.

I gave up and bought a 10-22, despite the fact that I think the 10-20 is at least as good. One hopes you'll have better luck.
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