Decentering?

Would love to hear feedback on this one. These are from my Sigma 10-20 EX. Lately I've noticed a "smear" on the left side of the images at certain apertures, usually around F4-f6.3:

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Another tripod-mounted sample:

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Mike55 wrote in post #13937462
The right side is simply superior to the left. It's not razor sharp or anything, but the left is just messed up. Sigma repair told me this was "normal" after I sent the lens in.

No, it's not, demand repair or replacement. Most of the times it's hard to convince Sigma techs that this is lens at fault, not your technique, camera body or else, just ask for supervisor.

Thx.

I asked for a supervisor and the guy told me there was no one higher. Then he told me that I shouldn't be shooting at F4. I included a CD of example photos and the original receipt which indicated the lens was under warranty. When they received the box, they told me nothing else was in it, no cd, no receipt from Amazon, and that I had to pay for the repair. I told them it was an EX lens and I sent the receipt. they said it wasn't there. So I immediately sent them a jpg of the receipt, which they finally acknowledged. The "tech" told me the lens was perfectly fine. Amusingly enough, when they sent the unfixed lens back to me, the box included my example CD and the copy of the receipt....

I have the same similar problems with the f/3.5 version. Also, what is your version.

I've owned 3 copies of the Sigma 10-20 - 2 had issues and 1 was OK. One had the exact same problem as you and I returned it (hope they didn't repackage it and sell it to you!). The other had a loud grinding AF. I sent a video of it to Sigma and they said it was normal, go figure.

EngrChris wrote in post #13937769
I have the same similar problems with the f/3.5 version. Also, what is your version.

The 10-20 4-5.6 EX. Did you send yours in yet? I have to say, this experience with Sigma repair is pretty much making sure I never buy anything from them again.

Left hand side softness is the achilles heel of the 10-20 Sigma

My father has one that is pretty much perfect. I should swap them when he isn't looking on our next trip, lol.

Mine has the exactly same defect as yours except mine is soft on the right side and stopping down doesn't help much even at f/8. I sent in for calibration once and got it back without any noticeable improvement. It seems to get sharper if I use MF and set to infinity.

Could it be field curvature, or just a bad lens?

Well I haven't seen any of the Canon or Tokina owners complaining about this.

I had mine for 6 months before I used it. I didn't notice it in every shot so I was blaming myself at first. Then I took a shot which it was horrendously bad, so I took back to the shop I bought it from. It couldn't be fixed in the UK and had to go to Japan.
Where I bought it from, "Jacobs" in Cardiff, got Sigma to exchange it for a new one which is very sharp. I am a happy owner now

h14nha wrote in post #13938043
I had mine for 6 months before I used it. I didn't notice it in every shot so I was blaming myself at first. Then I took a shot which it was horrendously bad, so I took back to the shop I bought it from. It couldn't be fixed in the UK and had to go to Japan.
Where I bought it from, "Jacobs" in Cardiff, got Sigma to exchange it for a new one which is very sharp. I am a happy owner now

Nice. That's the thing, you don't notice it in every shot. My copy is actually sharper than the 10-22's I've tried, except for the far left side. I finally had enough when it ruined a bunch of astral shots.

Holy sh$#$.

Amazon freaking rocks. Just got off the phone. They are honoring the warranty and sending me a new replacement tomorrow. All I have to do is send the old lens back.

I bought it in 2009.

Thank you, Amazon.