Summary: I own the old version of this lens Sigma 17-70 F2.8 -4.5 and love it. I bought this new version hoping to get a better one. Once I got this lens, I tried shooting it and found that when you try to take a macro picture, it will not focus where you want it to be. It will always be in the front of the point it is intended to be. Although OS is incorporated with this new version, this glass is heavier than the old version.
Summary: Save your money and do not buy this (short and sweet). I returned the first one and the replacement was also a disappointment. It's just not worth your time and money to be playing around with a bad lens (period). Reviewer wrote Oct 7th 2010: What an idiotic review! Are you 12? Oct 25th, 2010 Sorry about that. I just got back into this account after enjoying the whole summer traveling and just didn't realize that people had so much passion about review boards.
Summary: I bought this lens to take on vacations, and as a general walk around for my Canon T1i. I wanted to be able to take landscape shots, have a little reach on the tele end, and the macro was a bonus. I've never purchased a non Canon lens before, but heard good things about the previous version of this lens. First thing I noticed, the lens does not fit onto the camera with the ease that a Canon lens does. It goes on, but required significant more torque, and this worried me.
Summary: This is probably the last time I try a sigma lens. I previously got the older non-OS 17-70, and it was not very sharp. This time, I was very excited to see if the newer product fared any better. But no, clearly this new lens, straight-out of the box, was focusing at a point in front of the intended target. This problem was made even more obvious when I immediately switched to my trusty Canon 17-55. Oh well...
AF problem was a shame when it took such sharp images
3 March 2013
Summary: Bought this lens from amazon warehouse and was excited when it arrived. However putting it on my Nikon D200 this excitement soon changed to annoyance as I quickly realised something wasn't right. The AF would continually search even when it was pointing at a still object, it was even worse under artificial light indoors. I tried the lens on my spare D50 and the problem still persited. I have since sent the lens back and won't be ordering a new one.
Summary: I'm sure this is a great lens, but the auto-focus system does not get on well with a Canon EOS 40D - specifically the lens spends a lot of time "hunting" for focus. I upgraded from the original non-OS non-HSM version of the lens, but now I've gone back to that lens. Maybe the HSM is just too fast for the older EOS models!
Summary: On a D5100: The autofocus is inaccurate (about 3 inches off each time) and fails in average indoor light. When manually focused at f/4, the results are sharp at the short end. I had the Sigma 150-500mm, and decided to order this (17-70mm) and the 70-300mm as Christmas presents. While the 150-500 is a great lens, the build quality and image quality on the latter two is disappointing.