Canon ef s 17 55mm f28 is usm change your view not your aperture with a constant f28 aperture throughout the zoom range and a 3 stop image stabilizer the ef s 17 55mm f28 is usm provides outstanding performance and framing flexibility in low light conditions wide angle zoom for ef s mount bodies f28 aperture throughout zoom range 3 stop image stabilizer fast quiet auto focus super spectra coating circular aperture for pleasing background blur passes distance inform