Summary: The problem was the overly tight mount. compared to all my other lenses, this one was so tight, I was afraid something would break. I returned it and bought the Sony 35 1.8 and am very satisfied. I have many Sigma lenses, but this one just did not work out.
Summary: I had this lens for a year and a half and I wanted to love this lens. I gave it every opportunity and it did take a couple of great pictures but, it let me down in the end. The pictures that I took with it, didn't come out as crisp as I expected and maybe that is my fault for expecting so much. In the end though, I had to sell the lens, it didn't do well in low light, never became my primary lens that I had hoped when I bought it.
Summary: Very good picture and build quality. However, my copy kept producing pictures with a noticeable black spot in the center. When I examined the lens, there was a large speck of dust trapped inside the lens. Returned for a full refund. Unfortunately the only other alternatives are the Sony SEL30M35 30mm f/3.5 e-mount Macro Lens (slightly more expensive but quality isn't as good) and the Sony SEL35F18 35mm f/1.8 Prime Fixed Lens (more than twice the price of this lens), so I...
Summary: I would not recommend this lens over the 14-42 II kit zoom from Olympus. The sharpness is lackluster and a little worse than the kit zoom, flare is a problem and CAs are prominent. It isn't really much of a bargain when you consider it's only 1 stop faster than the kit lens. I highly recommend saving for a better lens, like the incredibly good Panasonic Leica 25mm f/1.4, or the Olympus 17mm f/1.8. You'll be glad you did.
Summary: .......and to make matters worse, Amazon's systems are so pathetic they have now asked me to review it! OK here goes. It looked great, but it wouldn't fit my camera. It was a Sony-fit version.