This T Speed Booster Ultra 0.71x Adapter from Metabones allows a full-frame Canon EF-mount lens to be used on a Canon RF-mount camera. While providing a one-stop increase for the camera over the lens's aperture range, up to a maximum output aperture of f/0.9, the adapter's optics help to maximize the connected lens's apparent angle of view during UHD 4K video capture.