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Metabones Canon EF Lens to RF-Mount T CINE Speed Booster ULTRA 0.71x Adapter (EOS-R)

BH #MESPEFEFRBT2 • MFR #MBSPEF-EFR-BT2
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Metabones Canon EF Lens to RF-Mount T CINE Speed Booster ULTRA 0.71x Adapter (EOS-R)
Key Features
  • Makes Lens 0.71x Wider
  • Aluminum Alloy and Brass Construction
  • Satin Surface Finish
  • Positive-Lock EF Lens Mount
Use this Metabones Canon EF Lens to RF-Mount T CINE Speed Booster ULTRA 0.71x (EOS-R) 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 to support the newly EOS C70 (Super 35mm sensor). The field of view is now much closer to still photo mode. The Speed Booster is not intended for still photography but will work if the camera is configured to APS-C mode. It uses an advanced 5-element/4-group optical design by Caldwell Photographic, incorporating ultra-high index, tantalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion, and reduced vignetting. The 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. It has a design that 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. 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 including 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.
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Metabones MBSPEF-EFR-BT2 Overview

Use this Metabones Canon EF Lens to RF-Mount T CINE Speed Booster ULTRA 0.71x (EOS-R) 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 to support the newly EOS C70 (Super 35mm sensor). The field of view is now much closer to still photo mode. The Speed Booster is not intended for still photography but will work if the camera is configured to APS-C mode. It uses an advanced 5-element/4-group optical design by Caldwell Photographic, incorporating ultra-high index, tantalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion, and reduced vignetting. The 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. It has a design that 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. 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 including 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.

Mechanical
  • Patented positive-lock EF lens mount
  • The tripod foot is detachable and compatible with Arca-Swiss, Markins and Photo Clam ball heads
  • Flocking to reduce internal reflection
  • Satin surface finish
  • Aluminum alloy and brass construction with chromium plating
  • Rubber gasket protects the RF mount connection from dust and moisture
Electronic
  • Autofocus 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
  • It is powered by the camera body as with most lenses, no external power source required
  • LED indicator shows communication status
  • Build-in multi-function control wheel (turn/ push-in) for assignable functions (eg. ISO, shutter speed or aperture control, depth-of-field preview)
  • Store EXIF data (lens name, focal length, and maximum/minimum aperture) for one manual lens in the adapter
  • Image stabilization (IS) lens support
  • Focal length and aperture are adjusted in EXIF
Optical
  • Increase maximum aperture by 1 stop with a maximum output aperture of f/0.9
  • Advanced 5-element/4-group optical design incorporating ultra-high index tantalum-based optical glass by Caldwell Photographic
  • Increase MTF and makes lens 0.71x wider
Compatibility
  • Canon RF camera (under APS-C crop mode)
  • EOS-R, EOS-RP, EOS-R5, EOS-R6, EOS-C70
  • RED Komodo camera
  • Canon EF-mount lens
  • Canon EF-extender (teleconverter)
  • Carl Zeiss EF-mount lens
  • Sigma EF-mount lens
  • Tamron EF-mount lens
  • Tokina EF-mount lens
  • Contax N mount lenses modified to Canon EF by Conurus
  • Contax 645 NAM-1 adapter modified to Canon EF by Conurus

Metabones MBSPEF-EFR-BT2 Specs

Item Type
1x Reducing Lens Mount Adapter
Camera Compatibility
Canon RF Mount
Lens Compatibility
Canon RF Mount
Magnification
0.71x
Electronic Communication
Yes
Optical Design
5 Elements in 4 Groups
Included Shims
Materials
Aluminum, Brass
Packaging Info
Package Weight
0.915 lb
Box Dimensions (LxWxH)
5.6 x 4.5 x 2.3"

Metabones MBSPEF-EFR-BT2 Reviews

Getting the most out of my Komodo thanks to this speedbooster

By Brandon
Rated 5 out of 5
Date: 2026-03-30

Bought this speed booster to use on my RED Komodo. Absolutely love it, some slight vignetting on wide lenses in 6k, but pretty minimal. I would definitely recommend.

Do Not Buy

By Devin
Rated 1 out of 5
Date: 2023-07-16

I bought this to use my Leica R's (EF mount) on my Canon C70. The mount makes certain lenses vignette that don't even vignette on my larger Alexa Mini LF sensor. The backfocus is off on certain focal lengths and I can't focus on my lenses deeper than 15-20 feet. I followed the instructions on their website to adjust the backfocus (even though they said it should never be necessary (why make it something that can be changed if it's not a problem your mount has). While attempting to adjust the backfocus the screw you need to tighten and loosen over and over again to set it correctly snapped off inside the mount and now I can't adjust it at all so I still can't use my lenses with this mount. Waste of $500. Get a mount that doesn't have any glass in it or any need to adjust backfocus. It wont vignette and you wont have backfocus issues.

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