Overview
The Fujifilm XF100-400mmF4.5-5.6 R LM OIS WR is a super-telephoto zoom for Fujifilm X-mount mirrorless cameras. It is the natural starting point for a search for a “Fujifilm 400mm telephoto lens,” although it is a zoom rather than a fixed-focal-length 400mm prime. On Fujifilm's APS-C cameras, its angle of view corresponds to approximately 152–609mm on full frame. That makes it useful for photographing distant wildlife, outdoor sports, aircraft, and other subjects that are difficult to approach.
Its main features include optical image stabilization, linear-motor autofocus, weather-resistant construction, and a tripod collar. Photography reviewers generally regard it as a capable native long-zoom option, with useful handheld stabilization and good image quality. The trade-offs are substantial size, a variable maximum aperture, and performance that depends partly on the attached camera. It is not a substitute for a fast professional sports prime when light becomes scarce.
Who it's for
This lens suits Fujifilm X-series owners who want substantial reach while retaining a flexible zoom range. The shorter end helps when an animal approaches or when you need to include more of a sporting scene. Compared with a longer super-telephoto zoom, the 100mm starting point can make it easier to locate subjects before zooming in. It is especially appealing for outdoor shooting in reasonable light, where its aperture is less restrictive.
Buyers should be comfortable carrying a lens weighing roughly 1.4kg before adding a camera. A supportive strap, monopod, or tripod can make longer outings more manageable. Bird photographers who routinely crop heavily may prefer Fujifilm's 150–600mm zoom, while hikers who value portability above maximum reach should consider the smaller XF70-300mm. Beginners can use the 100–400mm successfully, but tracking moving subjects at these focal lengths takes practice and appropriate camera settings.
Things to know before buying
Check that the listing specifies Fujifilm X mount: this lens does not mount directly on Fujifilm GFX cameras. Its maximum aperture changes from f/4.5 to f/5.6 as you zoom. Stabilization helps counter camera shake, but it cannot freeze a moving bird or athlete; fast shutter speeds may still require higher ISO settings. Autofocus tracking also varies with the camera body, firmware, subject contrast, and available light, so lens-only claims about action performance need context.
The lens accepts 77mm filters and supports Fujifilm's compatible 1.4× and 2× teleconverters, which increase reach while reducing the effective maximum aperture. Before buying, compare the delivered price, US warranty coverage, return policy, and included accessories. Distinguish new authorized-dealer stock from used, refurbished, and imported listings. Weather resistance is useful outdoors, but it does not make the lens waterproof or remove the need for sensible protection in prolonged rain.