Summary: I had all the 35's on the market even the new sigma A And although the sigma is tad sharper in canter, when viewing images side by side the Canon always pleases my eye the most. Also the bokeh is way more superior on the Canon Not to mention the sigma hunts for focus quite more and is not consistent focusing at different distances even after calibrating on their dock.
Excerpt: I have rented this lens many times in the past, and am very happy to finally own it. It's always in my bag if I'm unsure of how much distance I will have from my subject. It's a great up-close lens without getting too much distortion. Very sharp. Would definitely recommend it.
Pros: Consistent Output, Fast / accurate auto-focus, Strong Construction
Excerpt: I bought this to use side by side with the 24-105mm f/4 for my 5D Mark III. It is so gorgeous & tack sharp that I never want to take it off. I have been using it for many different scenes and nothing has disappointed me; landscapes, city/street scenes, & portraits. It's fantastic in low light, as well. Highly recommend.
Pros: Consistent Output, Durable, Fast / accurate auto-focus, Nice Bokeh, Rugged, Strong Construction
Excerpt: I shoot lifestyle, travel and portraits and this lens was bought so I'd have something faster than my 16-35 f2.8 in low light and as a 'walking around' lens. Just used it for the first time over the weekend while at a family wedding. I wasn't the wedding photographer (and I stayed out of her way. I am not a wedding photog) but shot casual family moments. Perfect. Crisp and sharp when I hit focus and easy to use, fast to focus and amazing in low light.
Pros: Fast / accurate auto-focus, Fast In Low Light, Nice Bokeh, Sharp, Strong Construction, Very quiet focus