Ring-type USM
The RF mount has a large 54mm inner diameter barrel and a short back focus distance of 20mm, which significantly increases optical design flexibility and supports the development of new and unique lens designs. This mount has the potential to develop large-aperture standard zoom lenses with a maximum f-stop of f/2, such as the RF28-70mm f/2L USM lens; Another notable feature of the RF mount and EOS R System is the new 12-pin communication system. It significantly improves communication speed by instantly transmitting large amounts of data between the lens and the camera, such as focus, zoom, aperture, image stabilisation settings, lens aberration, and data for digital lens optimizers (DLO). With these features, the system can achieve excellent image resolution and a beautiful bokeh effect with a large fully open aperture. The new control ring designed for the lenses also provides smooth operation. The RF lens series realises new possibilities, building on Canon's pioneering philosophy, which began with the EF-mount series.