Canon EF Lens to RF-mount T Speed Booster® ULTRA 0.71x (EOS R)

Key Features


  • Increase maximum aperture by 1 stop. (with a maximum output aperture of f/0.9).
  • Increase MTF (details).
  • 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).


  • 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 (see note 3).
  • 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).
  • Cinema EOS lens (CN-E 18-80mm T4.4 L) support with the supported camera (eg. EOS C70).
  • LED indicator shows communication status. 
  • Powered by camera body. With most lenses, no external power source is required.
  • Cinema camera Canon EOS C70 and RED KOMODO 6K and KOMODO-X support.


  • 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.



Speed Booster® ULTRA for RF Mount cameras

Sharper corners, less distortion, reduced vignetting

Metabones EF-RF Speed Booster®  ULTRA 0.71x - to adapt Canon EF mount full-frame lenses to the new Canon RF mount. Users are now able to mitigate most of the APS-C crop factor of  EOS R7/R10 (1.60x) and EOS C70 (1.45x) and reduce it to 1.14x and 1.03x respectively and support the RED KOMODO 6K Cinema Camera(Super 35mm sensor). The field of view is now much closer to the full-frame look. On the full-frame camera like EOS R5. R5c, R3, this Speed Booster is not intended for still photography but will work if the camera is configured to APS-C mode, and will work well with the specific video crop modes. For details of the crop factor by the camera and mode, please refer to the following table.

Speed Booster ULTRA uses an advanced 5-element/4-group optical design by Caldwell Photographic Inc., incorporating ultra-high index tantalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion and reduced vignetting. Speed Booster ULTRA has a magnification of 0.71x,  effectively reducing the crop factor of 4k video on EOS R and EOS RP from 1.75x to 1.24x. The Speed Booster ULTRA design makes very effective use of exotic materials at the furthest limit of glassmaking technology, and as a result is well corrected for use with virtually all full-frame SLR lenses regardless of exit pupil distance. Thus, the Speed Booster ULTRA performs extremely well with professional-grade f/2.8 zoom lenses such as the 24-70mm f/2.8 and 70-200mm f/2.8 zooms by Canon to produce 17-50mm f/2.0 and 50-142mm f/2.0 high-speed zooms, respectively. Similarly, high-speed fixed focal length lenses such as a 50mm f/1.2 will be transformed into a 35.5mm f/0.9 lens with excellent contrast and resolution from the center all the way to the edges of the image. (More information can be found in the press release here)


Crop Factor after using Speed Booster ULTRA 0.71x by camera


Metabones Canon EF Lens to Canon RF Mount T Speed Booster® ULTRA 0.71x


Compatibility List 
  • Canon RF APS-C camera:
    • EOS C70, EOS R7, EOS R10, EOS R50
  • Canon RF camera (under APS-C crop mode)
    •  EOS R, EOS RP, EOS R3, EOS R5, EOS R5C, EOS R6, EOS R6 mk2, EOS R8
  • RED Komodo 6K, RED Komodo-X (see note 6)
  • Canon EF-mount Lens
  • Canon EF-Extender (Teleconverter)
  • Carl Zeiss EF-mount Lens (see note 2)
  • Sigma EF-mount Lens (see note 2)
  • Tamron EF-mount Lens (see note 2)
  • Tokina EF-mount Lens (see note 2)
  • Contax N mount lenses modified to Canon EF by Conurus
  • Contax 645 NAM-1 adapter modified to Canon EF by Conurus


Unsupported List 
  • Canon EF-S Lens (see note 1 & 2)
  • APS-C Lens (except Super16 crop mode) (see note 2)
  • Lens correction such as peripheral shading, CA and distortion
  • Focus confirmation "chip" (e.g. Dandelion)
  • M42 screw mount adapters (see note 4)
  • Stacking non-Metabones/non-Conurus mount adapters on top (see note 5 and list of lenses which require modification below.)


Note :

  • 1. EF-S lenses do not fit on Speed Booster®. Some EF-S lenses may be modified to fit, but do so at your own risk.
  • 2. EF-S lenses and third-party lenses designed for APS-C format DO NOT WORK AT ALL when used in conjunction with Speed Booster® due to the limitation of image coverage.
  • 3. For use with fast lenses (faster than f/1.4), the pre-boost apertures will be displayed in the camera.

Slow lenses will report boosted apertures to the camera body but fast lenses will report pre-boost apertures. We won't show f/0.9 with a f/1.2 lens attached, but show f/1.2 instead.


a) EF 85/1.2L attached, camera display = f/1.2, physical aperture (lens + Speed Booster® combined) = f/0.85.

b) Sigma 35/1.4 attached, camera display = f/1.0, physical aperture (lens + Speed Booster® combined) = f/1.0.

  • 4. Some improperly-made M42 screw mount adapters may short the electronic contacts of the Speed Booster® and cause damage to the Speed Booster® and/or camera body.
  • 5. Many manual focus lenses (e.g. OM 28/2.8, OM 50/1.8, Leica R 15/3.5) have rear protrusions (spikes, levers, other appendages) which would damage the optics and/or housing of Speed Booster®  They need to be modified before they can be safely used on Speed Booster® Check and make sure there are no rear protrusions from the adapter/lens combination before using on Speed Booster®. Scratches and damages caused by rear protrusions on Speed Booster® are not covered by warranty.
  • 6. Add support for RED Komodo Camera from firmware version V1.50 of Speed Booster. Please check with RED on the compatibility of your EF mount lens with your Komodo camera. Some Tamron lenses may not work. Some lenses may have corner vignetting when used with Speed Booster ULTRA because Komodo's sensor is larger than APS-C.



To update the firmware of a Canon EF lens downloaded from Canon's web site, use Canon's own adapter. While a Metabones Speed Booster has been tested for this use case scenario it is not guaranteed to work and not supported.

List of manual focus lenses which REQUIRE MODIFICATION to be used on Speed Booster®

Many manual focus lenses have rear protrusions (spikes, levers, other appendages) which would damage the optics and/or housing of Speed Booster® They need to be modified before they can be safely used on Speed Booster® Check and make sure there are no rear protrusions from the adapter/lens combination before using on Speed Booster®. Scratches and damages caused by rear protrusions or by poor quality adapters are not covered by warranty. The following is an incomplete list of lenses known to be incompatible.

Leica R

Super-Elmar-R 15mm

Elmarit R 28/2.8

Elmarit R 35/2.8

Summicron R 50/2

Nikon F

20/2.8 AI-S

Olympus OM

OM 18/3.5

OM 21/2

OM 21/3.5

OM 28/2.8

OM 50/1.8

Pentax K

Every Pentax K-mount lens has a protruding fin and an aperture lever. It does NOT fit.




Remark: Your PayPal receipt is your order confirmation. There is no separate email confirmation until the shipment takes place.


Disclaimer: we are NOT licensed, approved or endorsed by Canon.

Why Metabones®?

Since its inception, Metabones has been designing and manufacturing lens adapters recognized among professionals and enthusiasts as leaders in design and workmanship.

Contrary to the popular trend of other factories using an aluminum ring painted black on the camera-body-side, we instead take no short-cut but use precision-machined brass with chromium plating on both the camera-body and the lens sides of our adapters, in order to ensure smooth mounting, great appearance, and durability. The lens side of the adapter features a strong leaf-spring structure, strengthening the adapter-lens connection and ensuring tightness of the lens in order to reduce wear and prevent focus errors and optical alignment issues from appearing.

Metabones uses matte-black treatment to keep internal reflection to a minimum in order to maintain the maximum optical quality possible with the lens.

All Metabones Adapters follow this tradition of uncompromising precision, robust build quality and outstanding finish. Our new Smart AdapterTM series of products add industry-leading electronic interfacing technology from Canada, with true electronic control of the lens' aperture directly from the camera body.


Our Smart AdapterTM  series adapters have the following additional features