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Sigma 10-20mm F4-5.6 EX DC HSM softness

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benjilafouine

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Hi,

Has anyone else noticed some kind of softness on the upper-right corner of the Sigma 10-20mm F4-5.6 EX DC HSM wide lens?

I took a landscape shot two weeks ago and found the upper right corner to say the least very soft at f8. The kind of annoying softness (almost like out of focus).

So I made a test today against a brick wall (at less than two feet from it). I used a solid tripod, and the 10 second timer to eliminate the possibility of hand shake (even if I have a very steady hand).

So here is the sample "as is" except for image size, including all the exif information (this shot was taken at 10mm at f8).



Since the problem is less obvious with the downsampled file, the original file is also available at the same paddress but with the " small" omitted (I did not want to annoy some people by posting directly a 3 megs + file).

Again, if I look at the upper right corner, I see softness. Has anyone experienced similar problems with this lens? Is it what I can expect from it? Should I do something about it?

I purchased this lens a while ago (maybe more than a year) but I haven't used it a lot until lately (probably the first time that I used a picture from it without cropping anything).

Thanks for your help.
--
Regards,

Benjilafouine
 
All the corners are a little soft, but you're right, the top right is definitely the worst. I've seen worse examples from this lens, where the whole side of the image is blurry. I think it's just the nature of the beast these days. It seems like more and more lenses have centering or corner issues. Perhaps it's because we can blow pictures up to 100% on our screens to examine them. Or perhaps it's because quality control is lower these days.

I'm not sure what Sigma considers as "within specs." Canon's specs are a sharp photo print at 8x10 inches viewed from a few feet away.

You have to decide if the corner softness is noticeable in print size of "real life shots" (brick walls are not real life shots) where it annoys you. If it is, then you have to decide if you want to send it to Sigma for an adjustment. In my opinion, the corner issue in your lens isn't all that bad. Almost no lenses have 100% symmetrical corners. Most lenses have some flaws, and if you go looking for them, you'll find them. Shooting brick walls is the best way to find flaws in even the most expensive lenses.

--
My gear is listed in my profile. My name is Jay.
 
In fact, I did not test for "testing purposes". I tested because I saw one of my real life image where the problem exist.

I really shows in the trees on the right this time, even if it is not at the top (but this shot was hand held if I remember well).

Here it is:



Same corner problem.

The original can be found at the same place without the small added of course.

Thanks for your help.
--
Regards,

Benjilafouine
 
That's pretty bad. There are others here who have reported similar right side softness. I'd send it in to Sigma for an adjustment.

--
My gear is listed in my profile. My name is Jay.
 
I spoke to someone at the store where I bought it. Turns out that this lens is under warannty in Canada for either 5 or 10 years.

All I have to do is to bring it back and it will be fixed/replaced by Sigma.

The specialist from the store told me that this was not a normal behaviour for this lens.

I'll drop the lens there today. I will miss it a little bit but it is not my main lens.

Thanks.
--
Regards,

Benjilafouine
 
This appears to be the most common problem with this lens. Some lens element is not positioned correctly, causing one side to be blurry. Oddly enough it always seems to be the righthand side...
The only thing you can do is have Sigma fix the problem.
benjilafouine said:
Hi,

Has anyone else noticed some kind of softness on the upper-right
corner of the Sigma 10-20mm F4-5.6 EX DC HSM wide lens?

I took a landscape shot two weeks ago and found the upper right
corner to say the least very soft at f8. The kind of annoying
softness (almost like out of focus).

So I made a test today against a brick wall (at less than two feet
from it). I used a solid tripod, and the 10 second timer to eliminate
the possibility of hand shake (even if I have a very steady hand).

So here is the sample "as is" except for image size, including all
the exif information (this shot was taken at 10mm at f8).



Since the problem is less obvious with the downsampled file, the
original file is also available at the same paddress but with the
" small" omitted (I did not want to annoy some people by posting
directly a 3 megs + file).

Again, if I look at the upper right corner, I see softness. Has
anyone experienced similar problems with this lens? Is it what I can
expect from it? Should I do something about it?

I purchased this lens a while ago (maybe more than a year) but I
haven't used it a lot until lately (probably the first time that I
used a picture from it without cropping anything).

Thanks for your help.
--
Regards,

Benjilafouine
Click to expand...
--

Slowly learning to use the DRebel (only around 29.000 shots) and now also the Fuji F11.
Public pictures at http://debra.zenfolio.com/ .
 
Over here, the warranty is seven years so I am fully covered. I will drop it today at the store.
--
Regards,

Benjilafouine
 
It is very difficult to achieve proper alignment to test for uniformity across the frame. The camera (sensor) needs to be perfectly parallel to a perfectly flat target. Proper lens tests are done with resolution charts many times mounted on thick glass panels for optimum flatness. The camera is then very precisely positioned to the target to ensure the sensor is parallel to the target in both planes. Using a small mirror against the center of the target helps with alignment. Although your alignment looks pretty good the test is not really conclusive unless you're getting similar results stopped down at f8 or smaller.

Bob
--
http://www.pbase.com/rwbaron
My PBASE page is new and growing so please be patient.
 
mine actually is soft on the left
but I don't really care... i always use the right side or center for composition
i love this lense too much to send it to sigma for 2+ weeks
 
In my case, it is 4 to 6 weeks!!! I finally kept with me for the summer and will have it calibrated in the fall. I have been told that it can be improved over it present condition.
--
Regards,

Benjilafouine
 
There is a relatively easy test that I have used and that works very well: take a picture (with high shutter speed), then turn the camera upside down and take the same picture again. For best accuracy in this test you switch to manual focus after the first image and do not refocus so as to not have a difference in focusing. Also, do this with a landscape, with focus close to infinity so a slight movement forward or backward doesn't matter either.

This test made very clear that my first Tokina 12-24 had a soft righthand side. With a properly aligned lens both images (up to rotation) should be identical. In my case one was soft on the righthand side and the other on the lefthand side.
rwbaron said:
It is very difficult to achieve proper alignment to test for
uniformity across the frame. The camera (sensor) needs to be
perfectly parallel to a perfectly flat target. Proper lens tests are
done with resolution charts many times mounted on thick glass panels
for optimum flatness. The camera is then very precisely positioned
to the target to ensure the sensor is parallel to the target in both
planes. Using a small mirror against the center of the target helps
with alignment. Although your alignment looks pretty good the test
is not really conclusive unless you're getting similar results
stopped down at f8 or smaller.

Bob
--
http://www.pbase.com/rwbaron
My PBASE page is new and growing so please be patient.
Click to expand...
--

Slowly learning to use the DRebel (only around 29.000 shots) and now also the Fuji F11.
Public pictures at http://debra.zenfolio.com/ .
 
I can't say mine is soft, but I find that I have to have very special lightning and subjects for the picture to turn out right. It's not as sharp has I expected it to be...

This is the only good shot that I managed to achieve so far, in 2 months of use,



If you want, I can post 100% crops, just say the word.

Best regards,

--
d i o g o c a r v a l h o - nature images

 
UWA lenses are a tough beast to master. I've owned the Tokina back in my Nikon days, and I tried out the 10-22 Canon. I would say my talent is lacking, not the lenses. Although, my Canon was severely decentered and had to go back.
guizang said:
This is the only good shot that I managed to achieve so far, in 2
months of use,
Click to expand...
--
My gear is listed in my profile. My name is Jay.
 
That is an interesting idea... However I will go in another direction for the next month or so: close down to f11 or use it at 12mm in the hope that it will perform better. Like I said in my other thread, I do not want to loose this lens for the summer time and I will have it fixed in the fall (7 years warranty, so no rush there...)

I received this morning very interesting comments at the store where I bought it (here is the picture again for easy reference).



Like they said, this is clearly a lens problem because the far right side at middle height of the image is blurry (the trees) while the front ramp in the lower right portion is not blurry. This is then clearly in their opinion not a DOF problem.

Since I know that this bluriness does not come from the camera itself (after more than 4500 shots with various lens) this only leaves the lens as the problem.

And they believe that this is not a normal behaviour issue. It has to be fixed. If someone is interested, i'll post some 12mm or 10mm stepped down (f11) shots in a few days just to see if it helps me in the mean time that I get it fixed.

The diagnostic is never easy...

--
Regards,

Benjilafouine
 
Just got the lens back from the store today. Seems like a back element was misaligned. Now I need to run a few tests. I'll post them as soon as the're done.
--
Regards,

I may be wrong, but I may be right.

Benjilafouine
 
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