This lens is ultra wide with less price compare to EF16-35mm f2.8L and 17-40mm f4L but the same result at middle apertures. Great if u stop down at F16 and can focus close to 8 inches with a wide angle perspective.If set wide open outdoors pictures are crisp and sharp and in low light. It's lighter and weighs 14.3 ounces. There is some vignetting on corners if set to F4-f5.6 with an external flash if focus at 10'. Slight distortion is expected on architectures but I'm not surprised. Over all, It's an awesome lens. It's mounted on my 1D MII most of the time to give a 26mm result. If mounted on a Full frame, i.e. 1DS, there's CA. I recommend this lens.
Pros: Fast Auto-Focus, Great Bokeh, Beautiful Colors/Contrast, Good Low-Light Performance