Sigma 10mm - 20mm f/4-5.6 EX DC HSM Autofocus Zoom Lens for Canon EOS Digital SLR Cameras.
Really great lens
Pros: Consistent Output, Nice Feel
Best Uses: Landscape/Scenery, Cityscapes, Night Photography
Describe Yourself: Photo Enthusiast
Was this a gift?: No
I've owned this lens for several years. I always have this lens handy when I travel from my home. It is that good. This is my really go to lens when I want to get really wide. I mean really wide the first time I used it I realized I was seeing the leg of my tripod in the bottom of the frame! I have it on a 40D with a battery grip and that works well for me. I've read the reviews about the f-stop not being wide enough. I tend to shoot around 5.6 or 11 so that isn't an issue with me. Landscape photography at night it's on a tripod anyhow.
Barrel distortion? Yes, sometimes but then again when you go this wide you've got to expect it. Just learn to work around it.
Bottom line is I really like this lens so much that when I went to a full frame I still bring this lens with me on my 40D. Going to have to look into a 17-40 lens for that. I'll lose a degree on the low end but I think I can live with that.