In addition to being Canon's newest super telephoto lens, the EF 400mm f/4 DO IS II USM is also the most recent diffractive optics lens, which strives to lighten the overall weight of such a focal length through the use of a specialized optical design. Featuring gapless dual-layer diffractive optics, along with a large-diameter aspherical element and one UD (Ultra-Low Dispersion) element, chromatic aberrations and diffraction are well controlled. Optimized lens coatings also help to reduce flare and ghosting for increased contrast and color neutrality. Protective fluorine coatings have been applied to both the front and rear elements, which pair with an overall weather-resistant construction for use in adverse conditions.
In addition to the lighter weight the diffractive-optics design affords, this updated model also incorporates a refined Optical Image Stabilizer to compensate for up to four stops of camera shake to better enable handheld use. Three dedicated image stabilization modes—standard, panning, and during exposure only—support a variety of shooting types, and the Ultrasonic Motor and Power Focus mode complement fast focusing performance and natural handling abilities. Ideally suited for wildlife and sports photographers, this apt super-telephoto lens benefits those looking for a quick, responsive long lens featuring a lightweight, yet optically refined design.