The Kenko Tokina 17-35mm f4 Pro FX lens was first seen on February 2011 at CP +2011, The Tokina 17-35mm f4 lens release dates are now confirmed, July for the Canon mount and September for the Nikon mount.
Read more about the Lens here(google translated) http://bit.ly/lqJQ3w
See the Sample Images here www.kenko-tokina.co.jp/tokina/atx17-35.html