Canon came out with it's stellar 16-35 initially in 2001. As seen in this Wikipedia article, there are currently three variations on this focal range available with the canon badge: The Canon EF 16-35mm Lens



The most recent, an f4 variant, was released in 2014 and is getting high marks for sharpness in most reviews I've read. It may be a stop less bright, but it has very good Image Stabilization (IS) that the others do not have.

Now, Canon Rumors is reporting that a fourth version of the Canon 16-35 is expected in June! You can read about it on Canon Rumors, here: Canon EF 16-35mm f/2.8 III Coming in June