An update to a venerable L-series zoom, the full-frame 16-35mm f/2.8 lens provides an extremely versatile range combined with a fast maximum aperture for excellent performance in a wide range of trying conditions. Version III offers an improved optical design that will provide notable improvements in outer and corner sharpness. Designed for use with full-frame DSLRs, this optic is compatible with APS-C format cameras as well where it will provide a 25.6-56mm equivalent focal length range. Constant f/2.8 maximum aperture offers consistent performance and excellent light transmission throughout the zoom range. Two large-diameter GMO dual-surface aspherical elements and one ground aspherical element help to minimize distortions throughout the zoom range in order to maintain edge-to-edge sharpness and illumination. Two UD lens elements are used to minimize chromatic aberration in the outer area at wide-angle; as well as eliminates color blurring around the edges of the subject, for images with high resolution and contrast. 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.