An amazing lens from landscape to portrait! Canon EF 17-40mm f/4L USM Ultra Wide Angle Zoom Lens L-series ultra-wide-angle zoom lens that's ideal for both film and digital cameras EF. Superior optics by the use of three Aspherical lens elements, in addition to a Super UD (Ultra-low Dispersion) glass element. Optical coatings are optimized for use with digital cameras. This lens focuses as close as 11 inches (0.28m), and offers both Canon's full-time manual focus and a powerful ring-type USM for fast and silent AF. It has a constant f/4 maximum aperture, and offers the choice of screw-in 77mm filters or a holder in the rear of the lens for up to three gel filters. Finally, it offers weather-resistant construction. * Focal length: 17-40mm * Maximum aperture: 1:4 * Lens construction: 12 elements in 9 groups * Diagonal angle of view: 104 to 57 degrees (at 30 feet) * Focus adjustment: Inner focusing system with USM * Closest focusing distance: 0.9 feet * Zoom system: Rotating type * Filter size: 77mm * Dimensions: 3.3 inches in diameter, 3.8 inches long * Weight: 1.1 pounds