Summary: For the money, you really can't beat this lens. I picked it up for about $50 and it's image quality is as good as the modern $100-$150 variety you can buy with AF (although that is still an amazing price point for the quality). It's lightweight, portable and manual focusing is pretty smooth. I bought this lens to fit in between my 35mm and 135mm primes. I own a Sony A7r. It shoots wonderfully wide open. Decent sharpness, smooth bokeh and fast.
Excerpt: This lens should be in every photographers bag, whether serious or hobbyist. Great lens and for the price, you cannot beat it. One thing tho is the build is very "Plastic Like" but for the price you should not expect it to be built like an L lens.
Pros: Consistent Output, Easily Interchangeable, Fast / accurate auto-focus
Excerpt: The price vs performance of this tiny lens is hard to beat. It's a very fast prime lens. However, to be at the price it's at, the build quality was sacrificed. The build material and zoom mechanism is not great. That said, it does what it does well. If you have a low budget like I do, this is a perfect prime lens for you.
Conclusion: I debated about purchasing this lens becuase of the plastic build quality, but I have been amazed at the sharpness and quality of the pictures - particularly for portraits. The super fast F1.8 lets you get that nice, short depth of field & bokeh, without spending $$$$. I also love the small and light package - it completely changes the feel of my 6D, making it feel much more compact, portable without getting the attention that some larger lenses get.