Canon RF Mount
Direct Answer
The Canon RF Mount (introduced in 2018 for the EOS R system) is a 3-tab full-frame mirrorless bayonet mount featuring a 20.0 mm Flange Focal Distance, a wide 54.0 mm inner throat diameter, and an advanced 12-pin high-speed data bus. Retaining the large 54mm diameter of the classical EF mount, it enables ultra-fast aperture lenses such as the RF 28-70mm f/2L and 50mm f/1.2L.
Source: Canon Inc. EOS R System Whitepaper / CIPA
Specs
| Flange Focal Distance (FFD) | 20.00 mm (0.787 in) |
| Inner Throat Diameter | 54.00 mm (2.126 in — identical to legacy Canon EF mount) |
| Bayonet Tabs | 3 asymmetrical stainless steel bayonet tabs with clockwise mounting twist |
| Electronic Interface | 12 contact pins (high-bandwidth bidirectional bus for lens control ring and Coordinated IS up to 8 stops) |
| Legacy Adaptability | 100% native AF/IS compatibility with all Canon EF/EF-S lenses via Canon EF-EOS R adapter (24mm spacer) |
| Lens Control Ring | Physical programmable control ring on all native RF lenses (aperture, ISO, exposure compensation) |
| Camera Systems | Canon EOS R5 / R6 / R3 / R8 / R, Cinema EOS C70 / C80 / C400, APS-C EOS R7 / R10 |
The 12-Pin High-Speed Bus
Canon upgraded from the 8-pin EF system to a 12-pin data communication architecture. This high-speed serial bus continuously exchanges optical aberration profiles, focal distance, and gyro vibration data with the camera DIGIC processor in real time, enabling Coordinated Image Stabilization (combining in-body IBIS with optical lens IS for up to 8.0 stops of shake correction).