CANON EF 17-40mm f4.0L USM
EF Mount L-Series Lens Aperture Range: f/4-22 Three Aspherical Elements, One Super UD Ultrasonic Autofocus Motor Manual Focus Override Water and Dust Resistant Internal Zooming and Focusing Truly Circular Diaphragm 77mm Front Filter Diameter Rear Holder for Three Gel Filters
The EF 17-40mm f/4L USM Lens from Canon is a high quality "L" series wide angle zoom lens for full frame and APS-C size DSLR cameras. It combines one high-precision molded glass aspherical element and two replica aspherical lenses to achieve the extended zoom range, while also correcting for common aberrations that arise during zooming. A Super UD (Ultra-low Dispersion) glass element minimizes the chromatic aberration of magnification which tends to occur with wide-angle lenses, to help eliminate color bleed along the edges of the subject and achieve high image contrast and resolution.
COLOUR CORRECTION
