Gitchigumi Loc: Wake Forest, NC

A couple of years ago, I purchased a Sigma 10-20 mm f3.5 wide angle lens. Two weeks ago, I was surprised by the lens not auto-focusing any more. Nothing I tried worked, including cleaning contacts, cycling the switches, etc.. It did focus manually, however. So, I sent it to Sigma for repair.

A couple of days ago, I received it back with a note that said: "Upgraded n/c". (Seriously, that is literally all that it said.) I have no clue what they did, but at least I didn't have to pay anything as it was still under warranty.

Now, I am struggling with getting it to produce sharp images. They all look "soft" to me. I tried to tune the lens in the camera (Nikon D7100), but that has been a disappointment. Maybe I need to work harder at it. The problem was the depth of field with my calibration setup showed soft focus across more depth than I thought I would get. So finding the sweet spot was elusive, if not impossible. Nothing appeared "sharp". My setup was for the lens at 15 mm, distance to target at 30" (50x focal length) and wide open at f3.5. I tried both auto-focus and manual-focus. They both look "soft". ISO was 100, but I tried higher. Shutter speed was 1/100th or higher. No joy.

This morning, I took some test shots of the back of the house, which was bathed in direct sunlight. I various focal lengths, ISO, shutter speed, etc.. None of those produced what I would consider a sharp image.

So, before I resign myself to accepting the soft lens, I thought I'd ask if any UHH folks have any experience with this lens. I can imagine that it would not be as sharp as a prime lens, but what is acceptable with a short zoom? Did I miss something with my test setup? Or, am I going off the deep end??

Thanks for your comments.

Eric2018 Loc: Los Angeles, CA, USA

I haven't had any similar experience.
Sounds like Sigma somehow messed up your lens. Have you communicated with the Sigma people?

grandpaw

I have had mine for years and it works fine. I have sold several 20x30 inch prints using this lens. Grandpaw

Bill_de Loc: US

Did you check the serial number to make sure you got your lens back?

Do you have a Sigma dock, or know someone who could loan you one?

If it was sharp before, definitely contact Sigma.

--

TriX Loc: Raleigh, NC

What are you using to do the MFA calibration? One thing I like about the Focal system is that the resulting graph of MFA vs resolution shows you exactly what the resolution is, so I know that if the number is 1250-1300, (or whatever), the lens is pretty sharp, while 800-900 not so much. It also gives you a way to compare not only resolution between lenses, but changes over time. Not a specific answer to your question, but suggesting a mechanism (other than “eyeballing it”) to check. If you are using Focal, what does the resolution show?

Gitchigumi Loc: Wake Forest, NC

Not yet... I just got it back on Thursday. Monday, will be my first opportunity.

Gitchigumi Loc: Wake Forest, NC

Yes... Same serial number, so assume the same lens.
No Sigma dock (will it work with this lens?)
I thought it was sharp before. I have not compared with older photos, yet.

Gitchigumi Loc: Wake Forest, NC

I'm not using the Focal system. I have a target setup where the target is perpendicular to the lens and there is also a graduated scale at a 45 deg angle, with the zero point at the center. Not a purchased gizmo, but one I made from a pattern downloaded from the internet. I can't post a photo of the setup at the moment, should have though. I'll do that as soon as I can.

TriX Loc: Raleigh, NC

I tried that also (made the system myself too), but while it works for lots of people, I always found it too subjective for me trying to judge exactly where on the scale was perfectly focused.

Gitchigumi Loc: Wake Forest, NC

I'll look into the Focal system...

Here is a sample image. It is a bit bright, as I was setup outside in the morning. The camera is on a sturdy tripod, mirror locked up... 1/1250 sec @ f3.5, 14 mm.

Attached file:
(Download)

AndyH Loc: Massachusetts and New Hampshire

Although I've heard of build issues on this lens, we are very pleased with ours. Good corner to corner sharpness, minimal chromatic aberration for a WA zoom of this range, and a very flat field.

I'd suggest sending back to Sigma. They seem to be quite responsible in their CS.

Andy

TriX Loc: Raleigh, NC

This is what a Focal readout looks like.

BTW, I downloaded your image and it looks “soft” to me as well.

(Download)

Gitchigumi Loc: Wake Forest, NC

Thanks for sharing the FoCal report. I like it, although it is a tad bit pricey.

TriX Loc: Raleigh, NC

Yes, the basic package which I have was about $60, and the professional version is more like $100, but when you pay thousands of $ for a collection of lenses, it’s not bad to make sure you get the best out of all of them. It’s saved me from returning two lenses which were unacceptably soft without MFA calibration.

Gitchigumi Loc: Wake Forest, NC

Good point!