Metabones T 0.71X Speed Booster Canon EF to RF mount 

Metabones EF-RF Speed Booster ULTRA 0.71x - to adapt Canon EF mount full-frame lenses to the new Canon RF mount. Filmmakers are now able to mitigate most of the 4k video crop factor of EOS R (1.75x) and EOS RP (1.63x) and reduce it to 1.24x and 1.15x respectively. The field of view is now much closer to still photo mode. This Speed Booster is not intended for still photography but will work if the camera is configured to APS-C mode. 60p FHD video does not work at all.

Optical:

• Increase maximum aperture by 1 stop. (with a maximum output aperture of f/0.9)
• Makes lens 0.71x wider
• Advanced 5-element/4-group optical design incorporating ultra-high index tantalum-based optical glass by Caldwell Photographic in the USA (patent granted)

Electronic:

• Autofocus.  AF speed is properly adjusted to account for and leverage the shorter focal length and the brighter maximum aperture
• Dual-pixel autofocus (DPAF) and video AF support
• Focal length and aperture are adjusted in EXIF
• Image stabilization (IS) lens support
• Store EXIF data (lens name, focal length and maximum/minimum aperture) for one manual lens in the adapter
• Build-in multi-function Control Wheel (turn/ push-in) for assignable functions(eg. ISO, shutter speed or aperture control, depth-of-field preview)
• LED indicator shows communication status
• Powered by camera body. With most lenses, no external power source required

Mechanical:

• The tripod foot is detachable and compatible with Arca Swiss, Markins and Photo Clam ball heads
• Flocking to reduce internal reflection
• Rubber gasket protects the RF mount connection from dust and moisture
• Aluminum alloy and brass construction with chromium plating
• Satin surface finish