Excerpt: This is my second sigma 17/50, and I am disappointed with the sharpness, the first one which I had problem with, the barrel getting loose was repaired and it did affected the sharpness, reason why I bought an other one, this new one is not any better??? I will trade for Canon lenses.
Pros: Great Stabilizer, Lightweight
Cons: Not sharp enough, Poor in Low Light, Weak Casing
Excerpt: Nice lens, easy to use and sharp, but not much more than the Sigma 18-250 mm f/3.5-6.3 I already own and use on a Canon 60D. I bought if for the larger aperture anticipating better IQ but found that a Fujifilm X30 28-112 mm with an f/2-2.8 lens that I bought later for travel use handled the larger...
Pros: Durable, Fast / accurate auto-focus, Smooth To Use
Excerpt: I purchased for indoor and outdoor use. F2.8 was the key, although the focal length was somewhat too short. I wish it could go up to 70 or 80mm. 50 mmm @ F2.8 was marginally better than my 18-200mm Nikor. It is also pretty heavy lens.
Summary: Does not work below 60F. Gives a lens error on my 70d, stops auto-focusing and won't release the shutter. Otherwise, it a fantastic lens. Very sharp and the OS works great. Update after 1 month: I'm returning it to see if I just had a bad copy.
Excerpt: It's a very useful lens for portraits, group shots and some landscape. But I have some problem with focusing. I think the auto focus motor is not very compatible with Nikon D7000. you should be really try hard to get tack sharp shots.