Canon EF 17-40mm F4L USM

The Canon EF 17-40mm f/4L USM Wide Angle Zoom is perfectly suited to professional digital imaging as well as use with 35mm and even APS SLRs. The optics are excellent, highlighted by three Aspherical lens elements, and one Super UD (Ultra-low Dispersion) glass element. A constant f/4 maximum aperture, moisture- and dust-resistant construction, and high-speed AF with a powerful ring-type USM are among its professional features.