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Metabones MB_SPEF-M43-BT4 Canon EF Lens to Micro 4/3 T Speed Booster ULTRA 0.71x

code: MB_SPEF-M43-BT4
  • £494.83
  • RRP: £527.64
Item Available | Usually dispatched within 24 hours


  • Increase maximum aperture by 1 stop.
  • Increase MTF.
  • Makes lens 0.71x wider.
  • Advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass by Caldwell Photographic in the USA (patent pending).
  • Electronic integration of aperture diaphragm, controlled by or from the camera body.
  • Partial autofocus support for late-model (post-2006) Canon-brand lenses.
  • Powered by camera body. No external power source required.
  • High performance 32-bit processor and efficient switched-mode power supply.
  • The tripod foot is detachable and compatible with Arca Swiss, Markins, Photo Clam ball heads.
  • Flocking material coating inside the inner hole to reduce the internal reflection.

Metabones MB_SPEF-M43-BT4 (MBSPEF-M43-BT4, MB SPEF-M43-BT4, MB/SPEF-M43-BT4, MB/SPEF/M43-BT4) MB_SPEF-M43-BT4 Canon EF Lens to Micro 4/3 T Speed Booster ULTRA 0.71x

Speed Booster ULTRA  for Canon EF lenses to Micro Four Thirds mount cameras, Sharper corners, less distortion, reduced vignetting 

New optical design: Advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion and reduced vignetting.

Like the revolutionary original Metabones Speed Booster announced in January 2013, the Speed Booster ULTRA has a magnification of 0.71x, and so it effectively reduces the crop factor of mirrorless cameras with DX-sized sensors, such as Sony E-mount and Fuji X-mount cameras, from 1.5x to 1.07x.  However, the new 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 fullframe 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 and Nikon 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. 

List of lenses with autofocus support on Speed Booster ULTRA:

Canon EF primes

  • EF 14/2.8L II USM
  • EF 24/1.4L II USM
  • EF 24/2.8 IS USM
  • EF 35/1.4L USM (Ver.19)
  • EF 50/1.2L USM
  • EF 85/1.2L II USM
  • EF 85/1.8 USM (Ver.18)
  • EF 100/2.8 USM macro (Ver.17)
  • EF 135/2L USM (Ver.17)
  • EF 200/2.8L II USM (Ver.17)
  • EF 300/2.8L IS USM
  • Extender EF 1.4x III
  • Extender EF 2x (mark I)

Canon EF zooms

  • EF 8-15/4L USM fisheye
  • EF 17-40/4L USM
  • EF 20-35/2.8L (Ver.18)
  • EF 22-55/4-5.6 USM
  • EF 24-70/2.8L USM II
  • EF 28-80/3.5-5.6 II (Ver.18)
  • EF 28-90/4-5.6 III
  • EF 35-350/3.5-5.6L (Ver.18)
  • EF 70-200/2.8L IS USM II
  • EF 70-200/4L USM
  • EF 70-200/4L IS USM
  • EF 70-300/4-5.6L IS USM
  • EF 70-300/4-5.6 IS USM
  • EF 100-300/5.6 (non-L, not USM, push-pull zoom) (Ver.18)
  • EF 100-400/4.5-5.6L IS USM


  • SP 24-70/2.8 Di VC USD A007 (Ver.15)
  • SP 70-200/2.8 Di VC USD A009 (Ver.31)

Tokina (full frame)

  • 28-80/3.5-5.6 (Ver.18)

Autofocus is DISABLED for the following lenses

  • Image stabilization (if supported by lens), auto aperture and EXIF work. Autofocus is supported only for those lenses marked with an asterisk (*), on NEX-5R/6, and with adapter firmware version 18 or above.

Canon EF primes

  • EF 14/2.8L (mark I)
  • EF 20/2.8 USM*
  • EF 24/1.4L USM (mark I)
  • EF 24/2.8 (old version, non-IS) 
  • TS-E 24/3.5L
  • TS-E 45/2.8
  • EF 50/1.4 USM
  • EF 50/1.8 II
  • MP-E 65/2.8 macro
  • EF 85/1.2L (mark I)
  • EF 400/5.6L USM

Canon EF zooms

  • EF 24-70/2.8L (mark I)
  • EF 24-105/4L IS USM*
  • EF 28-70/3.5-4.5 II 
  • EF 35-80/4-5.6 
  • Sigma (full frame)
  • 24-70/2.8 EX HSM
  • 24-70/2.8 EX DG HSM
  • 50/1.4 DG HSM (Ver.17)*
  • 50/2.8 DG Macro
  • 70-200/2.8 EX DG Macro HSM
  • 100-300/4


  • AT-X PRO 28-70/2.8

Zeiss ZE

  • ZE Distagon 15/2.8
  • ZE Distagon 21/2.8
  • ZE Distagon 35/2
  • ZE Makro-Planar 50/2
  • ZE Makro-Planar 100/2

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

  • Many manual focus lenses have rear protrusions (spikes, levers, other appendages) which would damage the optics and/or housing of Speed Booster ULTRA. They need to be modified before they can be safely used on Speed Booster ULTRA. Check and make sure there are no rear protrusions from the adapter/lens combination before using on Speed Booster ULTRA. 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.
  • Mount Type Canon EF Lens to Micro Four Thirds Mount

In The Box

  • 1x EF to MFT Mount Speed Booster ULTRA.
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