The EF 400mm f/2.8L IS III USM is a Canon L-series optic well-suited for outdoor, wildlife, and sports applications. This Super telephoto prime is designed for full-frame Canon EF-mount DSLRs, however can also be used with APS-C models where it provides a 640mm equivalent focal length. Fast f/2.8 maximum aperture benefits working in low-light conditions and also affords significant control over depth of field for working with selective focus techniques. Beyond the optical attributes, this 400mm f/2.8 is also characterized by its advanced five stop-effective Image Stabilizer system, which has three separate stabilization modes to suit various shooting applications. Also complementing handling, it comes with sophisticated ring-type USM, which provides quick, quiet, and accurate autofocus performance along with full-time manual focus override. Additionally, this lens is weather sealed for use in various environmental conditions, and it has a removable rotating tripod collar to benefit working atop a tripod or monopod.

Rounded nine-blade diaphragm contributes to a pleasing out of focus quality that benefits the use of shallow depth of field and selective focus techniques. It is Compatible with optional EF 1.4X and EF 2X teleconverters. It also features a fluorine coating on the front and rear elements to guard against water spots, smudges, or oil residue.