This high performance lens was designed with portability and handling ease in mind one super ud glass element whose characteristics are similar to fluorite and one ud glass element result in sharp pictures from corner to corner the lens also has a built in hood and a detachable tripod mount focal length and maximum aperture 400 mm f56 lens construction 7 elements in 6 groups diagonal angle of view 6 degrees 10 degrees focus adjustment inner focusing system with usm