Sigma 10-20: Soft Left Side?

Hi all, I hate to add to the litany of amatuer lens tests, but the return window on my lens is closing soon and I *THINK* I may have an example of this lens with the dreaded left side issues.

Here is a shot taken wide open at 10mm, on tripod using the self timer. To me, the left side looks significanltly different than the right. I don't claim to be a qualified tester of lenses, but I had noticed similar issues in "real world" shots. Any opinions? Send back to Amazon for exchange, or let Sigma have a look at it? Shut up and shoot?? By the way, stopping down seemed to help a bit, and the softness I am seeing was less aparent at 20mm. Thanks in advance for any advice...

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If you look for certain issues, you will find them. Was the camera perfectly aligned for the shot?

gasrocks wrote in post #5027613
If you look for certain issues, you will find them. Was the camera perfectly aligned for the shot?

I'm aware of the "seek and ye shall find" phenomenon. Thanks.

I highly doubt that the camera was perfectly aligned. This was a quick shot just to see if what I've been seeing in "real life" shots was visible on a boring brick wall. I take it you don't see the left side as markedly softer than the right? Cool!

ErikT72 wrote in post #5027671
I highly doubt that the camera was perfectly aligned. This was a quick shot just to see if what I've been seeing in "real life" shots was visible on a boring brick wall. I take it you don't see the left side as markedly softer than the right? Cool!

It may pay to reset up this photo with the camera aligned to the wall. The left side of this photo is quite soft, but may have been caused by the wall not being square to the camera.
I have just replaced my 28-135 as after 7 years of service, the left side of photos were suddenly very blurry.

Thanks for the replies, I will indeed set it up again and take special care to square things up.

i see a little softness, but i cant give any advice that hasnt already been given. If you dont mind me mentioning, you have very noticable distortions on the sides. I kinda came to the conclusion that the camera wasnt square, because distortion is also niticably different on each side.

if the fault still persists after you have run a thorough test it's possible it could be decentered, i had this on a 70-200mm.

Im pretty sure if it is decentered Canon service will be able to rectify it, chances are very high though it just wasn't square on as others have said.

Good luck with it.

EDIT: oops didnt see it was a sigma lens, same applies just sigma service lol

chris_arnet wrote in post #5027869
i see a little softness, but i cant give any advice that hasnt already been given. If you dont mind me mentioning, you have very noticable distortions on the sides. I kinda came to the conclusion that the camera wasnt square, because distortion is also niticably different on each side.

I don't mind you mentioning distortion at all, in fact, I kind figured that it was part of shooting at 10mm...
Is this not the case?
Anyway I'll shoot it again, thanks for the help....

The camera was tilted towards the right, and the right side is closer than the left side, so it is impossible to draw any conclusions from this shot.

Furthermore, the "left side" problem is not a problem only happening on the left side, it is a decentering problem, which may occur anywhere at the edges and corners.

Essentially it shows up as an area along the edge or a corner of the frame which is not sharp fully open while the rest of the picture is, and it often doesn't catch up with the rest of the picture when stopping down either.

First time I noticed this was with a TS-E 45, where it was the right corner. It didn't get better until F/8, and even then it was never as good as the rest of the picture. I saw this a second time with one of the three 85 F/1.8s I tried out, where it was the left lower edge, with a small piece of the corner. Same thing, it never caught up with the rest. I did notice that with manual focusing I could get the unsharp corners in focus, but in that case the rest of the picture wasn't very sharp.

If you have problems with aligning the camera with a wall, an alternative is using a double spirit level in the hot shoe, and turning the ball head so that the camera points down straight, with the levels indicating that the camera is perfectly aligned with the ground, or better, yet, a floor. Put a newspaper with small print under the camera, make sure th enewspaper lies down flat and that you don't have the tripod legs in view, and make some pictures at different apertures and zoom lengths with a remote release and MLU to make sure that this is the problem, if you do suspect you have it.

Do note that this lens suffers from some field curvature, but that means that unsharpness at the edges should be evenly spread around the edges, and that this should disappear (evenly) when stopping down the lens.

HTH, kind regards, Wim

Thanks Wim.
I'm going to retire from lens testing and just keep shooting with the lens.
I can always send it to Sigma later if I can't get comfortable with it.
thanks again,
E

ErikT72 wrote in post #5028055
I don't mind you mentioning distortion at all, in fact, I kind figured that it was part of shooting at 10mm...
Is this not the case?
Anyway I'll shoot it again, thanks for the help....

No, all lenses have distortion at UWA. I was pointing out how its different on each side, showing it wasn't squared. When my 10-22 gets here the first thing ill do is a brick wall test so i can have an idea about distortion with it.

I think that's you best bet. I had a Sig 17-70 that I thought had a focusing issue. After a few months of shooting with it, I sent it back to Sig for re-calibration. That sucker came back razor sharp & dead nuts on. Keep firing away & if you still have doubts, send it in. Only cost a few bucks for shipping for piece on mind...............

ErikT72 wrote in post #5029237
Thanks Wim.
I'm going to retire from lens testing and just keep shooting with the lens.
I can always send it to Sigma later if I can't get comfortable with it.
thanks again,
E

To me, it looks like the camera was tilted down a bit, which may result in the bottom being softer, but I do see that the left side is softer than the right on the bottom half of the shot.

If this is consistent, I do suspect decentering.