Wide-angle zoom 11-24mm f/4 lens is compatible with full-frame EOS DSLRs, as well as APS-C-sized sensors where it will provide a 17.6-38.4mm equivalent focal length range. Constant f/4 maximum aperture offers consistent performance and light transmission throughout the zoom range. One Super UD (Ultra Low Dispersion) and one UD element help to significantly reduce chromatic aberrations for improved clarity and color accuracy. Four aspherical elements help to minimize distortions throughout the zoom range in order to maintain edge-to-edge sharpness and illumination. Both a Subwavelength Coating (SWC) and an Air Sphere Coating (ASC) have been applied to lens elements to reduce backlit flaring and ghosting for maintained light transmission and high contrast in strong lighting conditions. A ring-type Ultrasonic Motor (USM), along with an internal focusing system, high-speed CPU, and optimized AF algorithms, are employed to deliver fast, precise, and near-silent autofocus performance. Full-time manual focus operation is available for fine-tuning of your focus position when working in the AF mode. A weather-resistant design protects the lens from dust and moisture to enable its use in inclement conditions. Additionally, fluorine coatings have also been applied to the front and rear lens elements for further protection against fingerprints and smudging. Nine rounded diaphragm blades contribute to a pleasing out of focus quality that benefits the use of shallow depth of field and selective focus techniques. Lens’ design accepts rear insert-type gelatin filters, which are cut-to-size and inserted behind the rear lens element.