With an effective focal length range of approximately 27-88mm (35 mm equivalent), the EF-S 17-55mm F2.8 IS USM is a powerful lens that delivers remarkable image quality. The wide angle zoom allows you to capture more of every scene and add a new sense of space and perspective to your photography. Fixed aperture The large F2.8 aperture provides excellent results in low light conditions. The aperture remains constant through the full focal length range, allowing you to zoom from approximately 27-88mm (35 mm equivalent) without slowing shutter speed. Pleasing background blur A circular aperture provides a pleasing background blur when shooting with a wide aperture; ideal for creating a sense of depth and isolating your subject from the background. Image Stabilizer The EF-S 17-55mm F2.8 IS USM features Canons 3-stop Image Stabilizer (IS). Ideal for handheld work, IS allows use of shutter speeds up to 3 stops slower with no perceptible increase in image blur. IS helps with low light conditions, fast paced scenes and shooting from moving vehicles. Fast, quiet auto focus A ring USM (Ultrasonic motor) uses ultrasonic frequency vibrations to drive responsive, near-silent high speed auto focus. Good holding torque stops the focusing lens group with precision without overshoot. Full time manual focus override is available without having to switch out of AF. Super Spectra coatings Optimised Super Spectra lens coatings and lens element shaping suppress flare and ghosting - more prone to occur with digital cameras due to reflection off the image sensor. Coatings also help achieve true colour balance and increase contrast for vivid hi-fidelity images. Passes distance information to E-TTL II The lens passes distance information back to the cameras E-TTL II flash system to ensure optimal flash metering in any shooting situation. EF-S Mount Lens 27-88mm (35mm Equivalent) Aperture Range: F2.8-22 UD and Aspherical Lens Elements Optical Image Stabilization... More