Does the Canon RF 400mm f/2.8 L IS USM take a teleconverter?
2 teleconverters are supported. A teleconverter multiplies the focal length and costs you light — and on a crop body the framing multiplies again.
Both converters are supported and both stay usable: 560mm at f/4 with the 1.4x, 800mm at f/5.6 with the 2x. On a lens this fast the 2x is the unusual case of a 2x that does not cost you autofocus.
| Teleconverter | Supported | Reach | Max aperture | On APS-C | On Micro Four Thirds |
|---|---|---|---|---|---|
| Canon RF Extender 1.4x | Yes — On Canon's Extender RF1.4x compatibility list. The 560mm at f/4 figures are computed, not Canon-published. | 560mm | f/4 | 896mm | — |
| Canon RF Extender 2x | Yes — The f/5.6 at 800mm figure is computed from the lens aperture, not a Canon-published number. Compatibility itself is on Canon’s extender list. | 800mm | f/5.6 | 1280mm | — |
What each converter gives you
Canon RF Extender 2x — 800mm at f/5.6 on this lens.
Canon RF Extender 1.4x — 560mm at f/4 on this lens.
The lens itself: Canon RF 400mm f/2.8 L IS USM · every Canon RF lens: Canon RF lens index · all teleconverter compatibility
Compatibility sourced from the manufacturers' own published teleconverter compatibility statements (manufacturer teleconverter compatibility statements (Sony, Canon USA, Nikon, Fujifilm, Sigma, Panasonic, OM System) — each row carries its own source URL) and verified 2026-09-02. Reach and aperture figures are computed from the lens's own published focal length and maximum aperture — a 1.4x multiplies focal length by 1.4 and costs 1 stop; a 2x multiplies by 2 and costs 2 stops. Lenses whose compatibility we could not verify from a manufacturer statement are omitted rather than guessed. Methodology