Excerpt: Using the sigma 17-50mm 2.8 on my GH4 and speedbooster S and it works great! Only complaints is that the Zoom ring has a little weight to it so Im hoping that loosens over time. Otherwise it turns smoothly once you figure its threshold.
Pros: Durable, Easily Interchangeable, Nice Bokeh, Rugged, Strong Construction
Excerpt: So far I have used this lens for both a wedding, and landscape shots while out hiking in the Pacific North West. It performs amazing! For the wedding it was a great wide lens for me to use during the ceremony, with minimal noise from the auto focus motor.
Pros: Fairly Silent, Fast / accurate auto-focus, Lightweight
Excerpt: This is an excellent lens. I upgrade this lens from the clasic 18-55mm 3.5-5.6f canon. The zoom is very quiet and the photos look very sharp and shoots very nice photos under low light. I am using the lens with my canon 7D.
Pros: Consistent Output, Durable, Lightweight, Strong Construction
Excerpt: I have several Sigma Lens,and decided to add this one to my bag.Great walk around lens,balances well on my D5100,solid build.Pictures come out sharp and very acceptical bokeh.Overall I would buy it again,great step up from a kit lens.
Pros: Fast / accurate auto-focus, Lightweight, Nice Bokeh
Excerpt: This is a very nice lens if your looking to upgrade from your kit lens. Images are sharp (except in the far corners), nice image stabilization, nice range. The only minor issue is that sometimes the autofocus is not as fast as you would like.
Pros: Durable, Easily Interchangeable, Nice Bokeh, Strong Construction