The EF400mm f/4 DO IS USM is the world’s first super telephoto lens incorporating the exclusive Canon-developed multi-layer diffractive optical element for camera lenses. The optical element, which incorporates light diffraction, is a major technological breakthrough, and it features an exceeding ability to correct chromatic and spherical aberrations and render high-quality images. By including this optical element in the lens design, the lens has achieved tremendous savings of 26% in overall length and 36% in weight compared to comparable lenses incorporating only conventional refractive optical elements. Moreover, the size and weight advantage comes at no cost to image quality, with the EF400mm f/4 DO IS USM delivering performance equivalent to conventional models in its class.