Summary: Bought this as a used lens. But have no problems with it other than auto-focus issues. It does not auto-focus easily. So I usually focus this lens manually. This is a great lens to use for kid photographs. Fast and wide enough to include kids up close without any visible distortions.
Excerpt: This lens is what I was waiting for a long time ago. Looking for different solutions including the Pentax 16-50mm F2.8 my choice fall on the Sigma and I can't tell you enough how happy I am with this lens. Very sharp, with portrait and close-up. Bokeh very soft and beautiful. The versatility of the focal length 24mm to 70mm is very usefull.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Nice Bokeh, Strong Construction
Summary: Having received the Sigma 24-70 f/2.8 this morning (after examining both the Sigma 24-70 and Tamron 28-75 at B&H), these are my two-cents: [Choice] I chose the Sigma over the Tamron, as IMO, HSM focuses quicker on my Pentax K-5II Body. I have a Sigma 50mm f/1.4 that I use for portraits and I am very satisfied with the fast focusing. I know I should not compare the focusing ability of either the Sigma 50mm F1.4 with another conventional focusing lens (e.g.
Summary: Just recently picked up the Sigma EX 24-60mm f/2.8 Lens for Canon used on eBay. Well, they don't sell it new any more new. I hear they sold off the stock for $200 before discontinuing it. I wish I knew about it then... Well, you can get one here or on eBay for below $300. Lenses similar to this would be Tamron 17-50mm or 28-75mm f/2.8, but only Tamron is full frame and 17-50mm can only be used on cropped bodies.
Excerpt: Of course the "gold standard" for a lens in the 24-70mm range is the Canon 24-70mm f2.8 Series II but for some of us it's price is prohibitive.<br />The Sigma 24mm-70mm f/2.8 EX Aspherical IF EX DG HSM Lens for Canon is a viable choice as are the samples from Tamron and Tokina. The Tamron, in my opinion, is also too expensive for what it is. The debatable advantage of the feature 'image stabilization' is marginal. Plus that increases the cost.
Pros: Fast / accurate auto-focus, Nice Bokeh, Performance, Price, Value