Canon RF Mount. The Canon RF 400mm f/2.8L IS USM belongs to Canon’s line of RF-mount lenses. It’s compatible with RF-mount cameras, but it doesn’t work with Canon EF-mount cameras.

Versatile Super-Telephoto Prime. This lens’s super-telephoto length makes it great for outdoor, sports, and wildlife photography. Its aperture is consistently bright, and its rounded nine-blade diaphragm gives you great depth-of-field control for selective focusing.

Redesigned Optics. This lens’s thirteen-group/seventeen-element optical formula includes Super Low Dispersion and fluorite elements that minimize chromatic aberrations and color fringing while providing high clarity, color fidelity, and sharpness. Canon has applied Super Spectra and Air Sphere coatings to the lens elements to further combat ghosting and flaring, even in harsh lighting.

Ultrasonic Focusing Motor. This lens uses a ring-type Ultrasonic Motor to provide fast, accurate, and nearly silent autofocus performance for both still and video shooters. You also get full-time manual-focus controlled by a customizable electronic focusing ring with three sensitivity levels, and a Focus Preset button to quickly recall a programmed focus position.

Optical Image Stabilization. The 400mm f/2.8L IS III’s built-in image stabilizer compensates for five stops of camera shake, so that you can shoot in lower light at slower shutter speeds without worry. You get three image-stabilization modes: standard single-shot mode, a panning-optimized mode, and a mode that only activates the stabilizer during the exposure.

High-Quality Build. This lens boasts a weather-resistant build that protects against the elements so you can use it in adverse conditions. This lens is extremely lightweight for a 400mm f/2.8, weighing in at a mere 6.4 lbs.