An excellent alternative to prime glass dollars, maybe.

I have always been a glass snob. Never have I shot anything but Nikon glass because THAT is what sees the picture, the camera only remembers it. That being said, my wife has a Nikon 12-24 and we often shoot together and sometimes need the same lens. A fellow shooter and Cannon lens snob spoke highly of the Sigma so I thought I would give it a try. The one I have kept is excellent even compared side by side to the twice the price Nikon. At 10mm it is still advisable to shoot at mid range apartures for edge to edge sharpness where this is not an issue with the Nikon lens. This is also the 3rd Sigma I have, the first two went back. I have heard from other sources that there are several inconsistancies with this lens and have found that to be true. This is a great product at a great price but buy it where you can shoot the lens before buying and are able to exchange if it is not right. This is a product where good dealer to customer service is important. All in all, this is not a use all the time lens by it's nature. And, it is an expensive product to manufacture by it's nature. Sigma gives you a huge bang for the buck with this not perfect but close lens at a price that makes this lens pratical to own at the price.