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.