canon ef 17-40mm f 4l usm ultra wide angle zoom lens for canon slr cameras
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 . in addition the lens focuses as close as 11 inches 0.28 mm 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