The EF 50mm f/1.2L USM Lens from Canon is a fast prime lens featuring a particularly large maximum aperture for effective low-light and shallow depth of field capability. As a standard focal length lens, it is suitable for most any shooting situation and its lens coating and optical construction are optimized to minimize chromatic aberrations, ghosting and flare. A truly circular diaphragm results in pleasing out-of-focus areas.An ultrasonic autofocus motor (USM) provides fast, smooth and quiet autofocus action and manual focus override allows for precise manual focusing even in AF mode. With a tight seal structure and the addition of the optional Canon protect filter, the 50mm f/1.2L lens is moisture and dust proof.