I don't shoot many photos from 17-24mm, unfortunately. When I do, there's rarely anything interesting in the corners. It's the worst part of the lens for distortion, although anything north of 20mm is pretty problem free. I find that it's pretty easy to get into the best part of the lens (30-40mm) by moving back a bit, which also allows you to get closer to hyperfocal distance for landscape shots.
Click on the photos to open the full-sized versions. Some may not be that great because I only venture into this focal range when I have no choice (for max sharpness, 35mm is the sweet spot). Try to draw the comparison across the frame.
These are probably some of my least interesting photographs. As I said, I only venture into this range when the other option is to not take the photo. All of these photos were shot with the K-5 IIs.
Here's some shot with the Sigma:
Minute Man NHP: 23mm, f/6.3, 1/100s, ISO160
Inside buildings at Greenfield Village:
17mm, f/5.6, 1/80s, ISO1600 19mm, f/5,6, 1/80s, ISO2000 23mm, f/8, 1/100s, ISO100
Here's one in Madison, WI:
21mm, f/5.6, 1/320s, ISO100
Here are some with the kit lens, 18-55mm f/3.5-5.6 II, all at Chaco Culture:
18mm, f/7.1, 1/250s, ISO100 18mm, f/5.6, 1/100s, ISO80 20mm, f/7.1, 1/160s, ISO80 21mm, f/8.0, 1/250s, ISO100 24mm, f/8.0, 1/200s, ISO100
You can see a
significant roll-off in sharpness with the kit lens. You don't see nearly the same thing with the Sigma, although I don't have any photos in similar light to the kit lens photos. I'll let you be the judge.
I can't do a perfect comparison because I no longer have the kit lens in my possession. It was strapped to my old K110D and given away to a family member, after I upgraded to the K-5IIs and this Sigma.