Unconventional in design and loaded with features, the Canon EF 400 mm f/4 DO IS USM Lens is the perfect choice for professional photographers. It is constructed with 17 elements in 13 groups, and offers a diagonal viewing angle of 6°. This lens features a multi-layer diffractive optical lens technology, which rectifies chromatic aberrations and minimizes the lens size to a great extent to deliver outstanding telephoto image quality. Use the image-stabilization function for reducing camera shakes by up to two stops whenever you are shooting at slow shutter speeds. This lens is constructed from magnesium alloy, which makes it lightweight, durable, and resistant to moisture and dust.