Review on Ultra Wide Angle Zoom Lens for SLR Cameras - Canon EF 17-40mm f/4L USM by Somsak Saladang ᠌

a good inexpensive lens, high-quality assembly (however, like all class L lenses), an excellent replacement for a regular lens on cropped cameras, it behaves like a good wide-angle lens on a crop. Sharp enough, I recommend it to those who shoot on a crop camera and are thinking about buying an L-class lens, but there is not enough money for more expensive lenses in this series. On a full frame, shoot from a focal length of 24-30 mm, the smaller picture in the corners is greatly distorted. I do not recommend full frame.