The 17-55mm zoom range delivers outstanding flexibility, producing high-quality images for landscape, portrait and travel photography. The f/2.8 aperture remains constant throughout the full focal length range, so you can zoom without slowing the shutter speed. With fast focusing in Ultra-Sonic motor (USM) technology you can roam city streets and expansive scenery, capturing subjects without interruption. The 3-stop optical Image Stabilizer and wide aperture reduces camera shake, enabling hand-held photography in low-light conditions or night photography without using a flash.