Canon RF 100-400mm F/5.6-8 IS USM

This Canon telephoto zoom spans 100–400mm for Canon RF full-frame cameras. That reach suits wildlife, outdoor sport and other distant subjects. A photographer can frame the whole scene at 100mm, then zoom to 400mm for a tight view of one animal or player. Canon introduced it in 2021, and it remains in production.

The main trade-off is aperture. The maximum runs from f/5.6 to f/8 across the zoom, which helps keep the barrel light. Photographers who need fast shutter speeds in poor light will feel that limit. Sunlit conditions suit it best.

At 1 lb 6.4 oz (635 g), the lens stays light for its reach, so handheld sessions remain practical. The barrel measures about 6.48 in (164.7 mm) long and 3.13 in (79.5 mm) wide. It scores 64/100 on our physical specification measure. Filters screw directly into the 67mm front thread.

The 100–400mm range makes distant subjects workable from one spot. A photographer can open at 100mm to show a bird within its habitat, then zoom to 400mm for a frame-filling view. Airshows and nesting birds also sit inside this reach. On a fixed sideline or hide, that flexibility beats walking closer.

Light is the constraint. The maximum aperture is f/5.6 at the short end and f/8 at 400mm. Bright days cost little here. In woodland shade or late afternoon, high shutter speeds for moving animals push ISO upward instead.

A distant background can still soften behind a perched bird, especially toward 400mm. Subject distance and background distance matter as well as aperture. Its optics specification score is 52/100.

Closest focus is 2.9 ft (88 cm) at 200mm. Maximum magnification reaches 0.41x at 400mm, where the minimum focus distance is longer. That magnification helps make a butterfly or lizard large in the frame.

Image stabilisation is built in, with Canon rating the optical system at 5.5 stops on EOS R and EOS RP bodies. It helps reduce blur from camera shake during handheld use. That support is useful at 400mm and can help you use slower shutter speeds when photographing still subjects.

A rotary zoom ring sets focal length. The zoom lock secures the lens at its retracted 100mm setting to prevent unwanted extension during transport. It does not lock every zoom setting.

Outdoor use has two gaps. The lens has no weather sealing, so dust and drizzle around a hide or shoreline call for extra care. It has no fluorine coating either. It scores 47/100 on our features measure.

The design includes aspherical elements and low-dispersion glass among its 12 elements in 9 groups. Aspherical surfaces help correct distortion and spherical aberration, which can bend straight lines and soften fine detail.

Low-dispersion glass helps reduce chromatic aberration, the colour fringes that appear along high-contrast edges. Birds against bright skies create exactly that kind of edge.