Excerpt: I was looking for a wide angle full frame lens but I could not afford the Canon 17-40 f/4L. or The Sigma 24-105mm F/4. So I did some research, asked other photographers and went to local camera shops. That is when I found the The Tokina 17-35mm f/4 Pro FX. It's a wide angle full frame lens.
Pros: Consistent Output, Fast / accurate auto-focus
Excerpt: Very clear, sharp results even at 17mm. A little slow at auto focus in low light conditions, but using it mostly outdoors for landscape it's not much of an issue. 82mm filter, would have been happier if it was 77mm.
Pros: Consistent Output, Durable, Easily Interchangeable, Strong Construction
Excerpt: I bought this lens as a cheaper alternative to Canon 17-40 f/4L. It is my second Tokina lens. I am not disappointed with this one. Overall build of the lens is excellent. It feels solid and mechanical performance is great. Lens is sharp for landscape and general, everyday ultra wide photography.
Pros: Durable, Easily Interchangeable, Strong Construction
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.
Excerpt: Made this purchase for landscape photography on and up coming trip. But used it at a recent air show with excellent results. Also comes in handy for shooting real estate. It is fast focusing and well built. The f4 aperture is not a problem on my Canon 5d mk3.
Pros: Fast / accurate auto-focus, Strong Construction
Excerpt: Everything else is excellent except that the auto fucos failed under extreme cold whether. Recently used in the snowy days, Vancouver, BC, this lens's auto focus became slower because of thermal contraction of the inner parts inside of the metal barrel, and finally stopped working.