A great lens, not quite as good as the new Leica 18mm, but much, much cheaper. This test was done on a Sony NEX 5n, so it will not represent true corner performance on a full frame. You can get an ides of the lenses characteristics though. The lens itself is tiny, it weighs 350g and is 71mm long. Distortion is well controlled, you can expect some lateral chromatic aberration in the corners, but it is easily corrected. Specs:

Aperture Range: F/4.0-F/22

Close Focus: 0.5m

Lens Elements: 10 in 8 groups

Coverage: 98 degrees – Horizontal plane, full frame sensor

Filter Diameter: 58mm

Construction: Metal, glass

Weight: 350g