Canon EF 17-40mm f/4L USM Lens - 8806A002

While an excellent ultra-wide zoom lens for film SLR cameras, the Canon EF 17-40mm f/4L USM Lens is especially well suited for use with EOS digital SLR cameras, which usually have an imaging sensor size smaller than the 35mm format. When used with such digital SLR cameras, the 17-40mm focal length range gives an angle of view approximately equivalent to that of a 27-64mm lens upon 35mm cameras, making it an ideal medium-aperture standard zoom lens. The EF 17-40mm f/4L USM, like all of the Canon "L" lenses, delivers optical performance equal to similar fixed focal length lenses, with silent, high-speed focusing.

Distortions and aberrations are remarkably small for a lens of such amazing capability. It combines 1 high-precision molded glass aspherical lens and 2 replica aspherical lenses to achieve the extended zoom range, while also correcting for common aberrations that arise during zooming. A Super UD (ultra-low dispersion) glass element minimizes the chromatic aberration of magnification which tends to occur with wide-angle lenses, to help eliminate color bleed along the edges of the subject and achieve high image contrast and resolution.