EF 17-40mm f/4 L USM

The Canon EF 17-40mm f/4L USM is a wide-angle zoom lens designed for full-frame Canon EF-mount DSLRs, though it also works with APS-C bodies where it provides a 27.2-64mm equivalent focal length. The lens features a constant f/4 maximum aperture throughout its zoom range, one Super Ultra-Low Dispersion element, and three aspherical elements that work together to minimize chromatic aberrations, spherical distortions, and color fringing for exceptional sharpness and clarity. A Super Spectra coating has been applied to reduce flare and ghosting in challenging lighting conditions.

The autofocus system employs a ring-type Ultrasonic Motor with internal focusing for fast, quiet, and precise focusing while maintaining full-time manual focus override. As a member of Canon's L-series, this lens is weather-sealed against dust and moisture for use in demanding environmental conditions. The lens has a 77mm front filter ring and includes a rear gel filter holder, with a minimum focus distance of 11.02 inches and a rounded seven-blade diaphragm for pleasing bokeh.