Canon's lightweight super-telephoto zoom for RF-mount, using diffractive optics for compact design.
The Canon RF 100-400mm f/5.6-8 IS USM was released in 2022 as a lightweight consumer telephoto zoom for the RF system, positioned as an accessible long-reach option for wildlife, sports, and travel photography. The variable aperture reaches f/8 at 400mm — a slow maximum aperture that enables the compact size and low weight by using a simpler internal construction. The RF mount's large diameter and short flange distance provide the optical foundation for the compact physical size despite the 400mm maximum focal length.
The optical design uses 12 elements in 9 groups. Nine rounded aperture blades produce smooth out-of-focus rendering. The 67mm filter thread is shared with several RF telephoto and mid-range zoom lenses, enabling filter carry-over across an RF telephoto kit. At 635g the lens is notably light for a 400mm zoom — the variable aperture extending to f/8 at the long end accounts for the compact proportions. Minimum focus distance is 0.88m. Nano USM motor provides fast, quiet autofocus suited to video use. IS is built in and rated at approximately 5.5 stops standalone. Dust and moisture resistant.
The f/8 maximum aperture at 400mm is the principal trade-off: in outdoor daylight exposure times remain workable, but indoor sports and low-light wildlife require elevated ISO or accepting motion blur at slower shutter speeds. On Canon RF bodies Dual Pixel CMOS AF operates reliably at f/8, which lifts the practical AF limitation present on older EF-mount bodies with f/8 AF sensitivity constraints. For wildlife in good outdoor light the 400mm reach at 635g is a practical field combination that heavier f/4-5.6 telephoto alternatives cannot match. On APS-C RF bodies the 640mm equivalent extends reach further for bird photography.
On the used market the RF 100-400mm is one of the more affordable RF telephoto options. Condition checks: IS operation (activate and observe stabilised viewfinder output), Nano USM response at 400mm (should be fast and near-silent), and front element for cleaning marks. The Canon RF 100-500mm f/4.5-7.1L IS USM provides weather-sealed L-series quality and additional reach at a substantially higher price. For photographers adding a first RF telephoto for wildlife or travel, the 100-400mm is the accessible entry point. Compatible with all Canon RF-mount bodies.