Canon EF 17-40mm f/4L USM Review
The Canon EF 17-40mm f/4L USM ($839.99 direct) is an ultra-wide to normal zoom lens that is compatible with Canon EOS SLR cameras. When used on a full-frame body, the lens provides an extremely wide 17mm field of view on the wide end with a 2.4x zoom factor that takes it to a normal 40mm field of view at the long end. It features a constant f/4 aperture and a silent focusing motor. The lens is a part of Canon's top-end L series of lenses—which are easily identified by the red band around the front element. It isn't as sharp as the Canon EF 16-35mm f/2.8L II USM($1,745.00 at Amazon), and is prone to showing color fringing around highlight edges. But if you're looking for an ultra-wide zoom and you're on a budget, some work in Lightroom can make up for its shortcomings.
The lens is short and squat at 3.8 by 3.3 inches (HD). It weighs about 1.1 pounds, and uses rather large 77mm filters. The lens can focus as close as 10.8 inches, regardless of the focal length. There's a large man...
The Canon EF 17-40mm f/4L USM lens is an inexpensive alternative to the 16-35mm f/2.8, but its edges are muddy at its widest angle.
Ultra-wide field of view; Reasonable price tag; Good center sharpness
Muddy edges and corners at 17mm; Some distortion; Noticeable color fringing