Sigma 10-20 Focus Issue W/Samples

I swear this lens is driving me insane. The issue seems to be focus-related. The problem shows up more at 20mm. I've tested it over and over and have never felt right about the performance. This is the one of my three lenses which I feel totally uncomfortable using.

Here's what I keep running into:

• Right side does not seem to focus at the same time as the left and middle.

• I can get the right side focused by setting the lens for a longer focus distance, but at the expense of the left and center.

• I can get the left and center focused by shortening the focus distance, but at the expense of the right.

I would like personal opinions as to what this might be caused by, and I would greatly appreciate any sharing of similar experiences. I currently I have little choice but to send it in to Sigma so they can evaluate it.

Thank You for your assistance.

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Swap your lens for another from your dealer. When built correctly the lens will have none of what you are experiencing. I have the Sigma 10-20 and it's perfectly even across the frame at all focal lengths. You seem to have the same complaint as some others.

I suppose it's some relief to know it's not an isolated incident. Thanks. I'll have to send it in because I bought it online. Quite literally, I couldn't afford the local stores' ~35% higher price.

I have heard that this is due to decentred elements, and unfortunately I have it too
I haven't had the best experience with Sigma, but it will take much more crap before I hand over twice as much for an equivalent Canon lens.

Edit: Removed "(hey wait, they don't even have an equivalent)". What was I thinking?

That's exactly what it seems like, the right side being more out of the proper distance relative to other elements than the left. The left and center have a similar, much deeper, more tolerant DOF overall, while the right is blurred almost all the time except in the focus distance "sweet spot"...which shouldn't be the sweet spot, and at which point the left and middle are totally soft.

As I said in another post, I got the chance yesterday to compare the canon 10-22 to my Sigma and the store's, and the center (and whatever side was clear) seemed sharper on the Sigmas.

I'm sorry; have you sent yours in? Mine's well under warranty (2 months old), and was DOA. I'm going to be sending it in as soon as the weekend's over. I don't know about you, but I can't live with, much less afford, $500 defects.

"I'm sorry; have you sent yours in?"
I haven't got around to it yet because it's not very noticable in my case, but I certainly will because I don't think it's acceptable.

It's very noticeable in my case. I almost can't believe they let it leave the factory, the way it is.

What I probably should've done in the first place was send it right back to the seller the moment I was dissatisfied with its performance...but I didn't know exactly what the problem was, and even after a few initial tests I still couldn't rule out user error.

I suppose that's what I have to do from now on: Test every lens extensively upon receiving it, and if something's amiss that I can consistently identify and recreate, send it straight back immediately.

I don't think this is the way it should be, having to carefully scrutinize each new lens to make sure it works as well as it's supposed to. That IS technically the manufacturer's duty to consumers, before the product even gets distributed, isn't it? What are we paying for, after all?

Sorry if I'm ranting, but the subject bothers me every time I think about it.

Resurrecting an old thread but wanted to keep the info in the same place.

I sent mine in to get fixed for the same problem, and it came back... the same. I bought it used so had to pay out of pocket for it. Quick shot of the calendar on my wall to illustrate the issue, notice the difference in sharpness between the left and right side of the frame.

Have a call into the service center to find out what the deal is. *sigh*

EDIT:
Handheld
Exposure - 0.02 sec (1/50)
Aperture - f/5.6
Focal Length - 15 mm
ISO Speed - 1250

this is a well known issue with that lens. IIRC I had to go through 4 of them to get a good one. If you are lucky to get a good one, it is a sharp lens. I sold mine long time ago. I only buy Canon lenses now.

what does it look like for real shots? i mean this lens isn't meant to be used on a small calender...

DreDaze wrote in post #16661493
what does it look like for real shots? i mean this lens isn't meant to be used on a small calender...

short answer is, even if you have the center dead focused even at say F8 to F13, one side of the picture is sharp and focused, but the other side will look out of focus, or like there is motion blur.

+++++++

Edit:
forgot to mention, on my first lens, I emailed pictures to Sigma and they acknowledged that one side is out of focus/less sharp than the opposit side.

sardines wrote in post #16661543
short answer is, even if you have the center dead focused even at say F18 to F13, one side of the picture is sharp and focused, but the other side will look out of focus, or like there is motion blur.

+++++++

Edit:
forgot to mention, on my first lens, I emailed pictures to Sigma and they acknowledged that one side is out of focus/less sharp than the opposit side.

i'm talking about joeblacks lens...not yours...

i know it's a problem that's happened before...but without knowing the settings of his shot above, he could just be shooting close to the MFD, or all kinds of other things that would lead to poor performance

and why would you shoot at f18?

DreDaze wrote in post #16661557
i'm talking about joeblacks lens...not yours...

i know it's a problem that's happened before...but without knowing the settings of his shot above, he could just be shooting close to the MFD, or all kinds of other things that would lead to poor performance

and why would you shoot at f18?

that's a typo supposed to be F8

DreDaze wrote in post #16661493
what does it look like for real shots? i mean this lens isn't meant to be used on a small calender...

DreDaze wrote in post #16661557
i'm talking about joeblacks lens...not yours...

i know it's a problem that's happened before...but without knowing the settings of his shot above, he could just be shooting close to the MFD, or all kinds of other things that would lead to poor performance

Updated my original post with settings, I thought about using a tripod and remote shutter release but then it wouldn't duplicate my real-world scenario. I guess the only thing I missed out on was using a flash.

I primarily use the lens for group photos in very tight spaces. In the samples below (I don't have the EXIF handy, I will update when I get to it) I am basically in between the group and a table of people at a bar. UWA distortion aside, there is noticeable softness on the right side of the frame.

#1

if it doesn't happen when on a tripod, and shutter release, i have to think the lens isn't the issue...but it is evident in those farther away shots as well