The Canon Mount Adapter EF-EOS R 0.71x lets EF-mount lenses fit RF-mount cinema cameras used with a Super35 sensor area — originally the EOS C70, and now supported on bodies such as the EOS C80. Its optical system increases the effective angle of view by a factor of 0.71x, offsetting the crop from a full-frame lens onto a Super35 frame, and increases maximum aperture performance by one stop in the process.

Electronic contacts maintain full communication between camera and lens, carrying metadata and supporting Dual Pixel AF with select Canon EF lenses. A secure-attachment mount, with four screws and a split locking collar, holds the adapter firmly in place on the body.