Ken Rockwell says this, but many think he is a little loopy but he has tried all the best lenses and tested them to some degree...
The 16-35mm f/4 L IS is Canon's best ultrawide lens for nature, landscape, interior, real estate, general architecture and outdoor photography because there is no sharper Canon ultrawide, and it's the only Canon ultrawide with
Image Stabilization (IS) so you can leave your tripod at home. It's also the lightest and least expensive of Canon's three sharpest ultrawides. The only other Canon ultrawides as good optically as this IS lens are the exotic
11-24mm and the new
16-35mm f/2.8 III — but neither has stabilization, and each is bigger and costs over twice as much!
While Canon's
17-40mm f/4 L and
16-35mm f/2.8 L II were the standards of the professional nature and landscape photography for years, they weren't very sharp in the corners — especially at large apertures. We always had to shoot them at f/11 for the best corner results. Many landscape professionals adapted the
Nikon 14-24mm and
Nikon 16-35mm lenses to their Canon cameras, or hauled the
huge manual focus Zeiss lenses instead. This new lens ends all that; it's sharp down to the pixels even in the corners
