Product DescriptionFrom the Manufacturer: Broaden your perspective with the Canon EF 17-40mm ultra-wide-angle zoom lens. Ideal for both film and digital SLR cameras, the lens offers three aspherical lens elements in addition to a Super UD (ultra-low dispersion) glass element, creating superior optics in all conditions.From the ManufacturerBroaden your perspective with the Canon EF 17-40mm ultra-wide-angle zoom lens. Ideal for both film and digital SLR cameras, the lens offers three aspherical lens elements in addition to a Super UD (ultra-low dispersion) glass element, creating superior optics in all conditions. In addition, the lens focuses as close as 11 inches (0.28mm), and offers both Canon's full-time manual focus and a powerful ring-type ultra-sonic monitor (USM) that produces fast and silent autofocus. Other features include a constant f/4 maximum aperture, the choice of screw-in 77mm filters or a holder in the rear of the lens for up to three gel filters, and optical coatings optimized for use with digital cameras. Boasting weather-resistant construction similar to other high-end L-series cameras, the lens carries a one-year warranty.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 A new and affordable L-series ultra-wide-angle zoom lens that's ideal for both film and digital SLRs. Superior optics are assured 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 similar to other high-end L-series lenses.About half the price of the 16-35 f/2.8 lens, this L-series lens has an entirely new optical design with three Aspherical elements and a Super UD-glass element. The combination provides superb contrast and sharpness, even at the widest settings. It's ideal for both film and digital SLRs, and features the same weather-resistant design, rear gel filter holder, and high-speed Ultrasonic Motor as the EF 16-35mm lens.What's in the box: Canon EF 17-40mm f/4L USM Lens,E-77U 77mm Snap-On Lens Cap,Lens Dust Cap E (Rear),EW-83E Lens Hood,Lens Case LP1319 and 1-Year Warranty.