Summary: I bought this specifically to do real-estate and events (I hate events so I refused to buy a 24-70). It is very sharp for those purposes and vary much rivals the nikon and canon equivalents for 1/3rd the price. Distortion is hardly a problem, which is not true for my other Nikon option. I will say it has some pretty obvious chromatic aberration but that's easily fixed on lightroom, photoshop, aperture, etc.
Summary: The item was as described and thanks to Amazon checking to make sure the lens was compatible with my camera. This made my purchase easy. It's a great wide angle lens, great for long exposures at night. The infinity setting is properly calibrated for easy use.
Summary: I bought this lens to use with my Canon 6D as a replacement of my Canon 10-22mm on a 7D. I'm pleasantly surprised at the quality and build of the lens for the price. Results are comparable to the Canon 10-22mm. Better build with good sharpness and low distortion. AF can be a little noisy but nothing to complain about. Seeing some CA but not as bad as in the Canon 10-22mm.
Summary: This lens is quite compact, though not very light weight, and solidly built like all other Tokina lenses. Optically it's superb. Very sharp and high resolution across the frame wide open. Best part is the distortion: probably the lowest among all FF UWA lenses, which means you can do architecture shots without having the stupid curved lines and having to do post processing to correct it. The filter is a little huge at 82mm.
Summary: First, this is for the Nikon Mount. I think Tokina's Canon mount appears to be less "sharp" than the Nikon mount. This lens is tack sharp wide open. I also have the 16-28 Nikon mount. Did a side by side comparison at F4. I was surprised that the 17-35f4 is sharper!!! What a pleasant surprise. The colors are not as good as the 168 however. Note: my copy of 168 is a good copy and considered ultra sharp until this lens.