More Views

  • METABONES MB_SPEF-M43-BT4 Metabones Canon EF to Micro Four Thirds Speed Booster ULTRA 0.71x

Metabones Canon EF to Micro Four Thirds Speed Booster ULTRA 0.71x


  • Increases maximum aperture by 1 stop
  • Increases MTF of any lens attached
  • Makes lens 0.71x wider
  • Patented 5-element/4-group optical design
  • Ultra-high index tantalum-based optical glass by Caldwell Photographic in the USA
  • Supports Autofocus (lens dependent)
  • Iris/aperture controlled by the camera body

Be the first to review this product

Exc VAT Price £606.38
Inc VAT Price £727.66

Available to order


The Speed Booster EF to Micro 4/3 ULTRA 0.71x Adapter from Metabones allows a full-frame Canon EF-mount lens to be mounted onto a Micro Four Thirds-mount camera. While doing so, the adapter's optics help to maximize the connected lens's apparent angle of view while providing a 1-stop increase for the camera over the lens's aperture range.

If a lens intended for 35mm film or similarly-sized full-frame camera sensors is connected to a camera with a Micro Four Thirds-sized sensor, it would project an image larger than the Micro Four Thirds sensor was built to accept. Able to capture only the center portion of the projected image, the effective angle of view of the lens would be narrowed, creating an in-camera "crop factor." The Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Micro Four Thirds-Mount Camera condenses the light from a lens designed for 35mm film or "full frame" camera sensors and projects it onto a Micro Four Thirds sensor. This allows a Micro Four Thirds sensor to utilize more of the light gathered by a connected lens, which effectively reduces the crop factor while making available to the sensor an additional 1 stop of light for each of the lens's f/stop settings.

This adapter is constructed from aluminum alloy for durability while minimizing weight and its mounting rings are made with brass to further prevent wear-and-tear. Inside are five lens elements in four groups that are designed to provide optical clarity as well as color fidelity, and a detachable tripod foot is included that features a 3/8" threads as well as compatibility with Arca-Swiss tripod heads.

The Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Micro Four Thirds-Mount Camera supports electronic communication between an attached camera and lens. Although the attached lens must be manually focused while using the adapter, aperture settings can be can be controlled from the camera. Also, if an attached lens is capable of generating EXIF metadata when used with a directly compatible camera, the Speed Booster Ultra 0.71x Adapter for Canon Full-Frame EF-Mount Lens to Micro Four Thirds-Mount Camera is designed to allow that information to be saved along with image files generated with a combination of the lens, a compatible Micro Four Thirds-mount camera, and the adapter.

  • Allows a full-frame Canon EF-mount lens to be used with a Micro Four Thirds-mount camera
  • Maximizes apparent angle of view of combined camera and lens
  • Provides a 1-stop increase for the camera over the lens's aperture range
  • Integrated jog dial for incremental aperture adjustment and push-button access to lens's widest aperture setting when used with a compatible Panasonic camera
  • Five lens elements in four groups for optical clarity as well as color fidelity
  • Supports communication between camera

Metabones Speed Booster ULTRA m43 Specifications:
Model Code: MB_SPEF-m43-BT4 (Canon EF mount), MB_SPNFG-m43-BM3 (Nikon F/G mount)
Color: Black Satin exterior; Black Matte interior
Magnification: 0.71x
Crop Factor for Full Micro Four Thirds format: 1.42x
Crop Factor with GH4 in Cinema 4k (4096 x 2160) Video Mode: 1.66x
Maximum Output Aperture: f/0.90 (with f/1.2 lens attached)
Rectilinear Distortion: < 0.7%
Lens Elements/Groups: 5/4
Length Reduction: 5.5 mm
Camera Mount: Micro Four Thirds
Compatibility: All Micro Four Thirds cameras are supported
Image Format: 17.3 mm x 13.0 mm (full Micro Four Thirds format)
Lens Mounts: Canon EF and Nikon F/G at release; other mounts to follow in the near future
Lens Compatibility: Any full-frame (36 mm x 24 mm format) SLR lens with the appropriate mount can be used. DX format lenses can be mounted but may result in vignetting when the full Micro Four Thirds format is used, depending on the lens. DX lenses are fully supported when used on the Panasonic GH4 in Cinema 4k mode, and will function without abnormal vignetting. Canon EF-S lenses are not supported, but third-party EF-mount APS-C lenses can be mounted and will have full electronic functionality.
Autofocus supported for Canon EF version subject to the following known limitations:
Contrast-detect autofocus support on Panasonic cameras only.
AFC (continuous AF) and AFF (flexible AF) modes are not supported.
Video AF may hunt more than a native lens.
Autofocus is not supported with previous generation Tamron VC lenses and Contax N lenses modified to EF mount by Conurus Canada. (Newer Tamron lenses such as the 24-70/2.8 VC A007 and 70-200/2.8 VC A009 work fine.)
Switching from manual focus or full-time manual focus (FTM) to autofocus may occasionally result in focus failing to lock or inaccurate focus. Activating autofocus for a second time will resolve this issue.
AF accuracy is lens-dependent. Special Features: Long-throw clickless aperture ring on Nikon F/G version; IS lens support, IBIS camera support, auto-exposure and in-camera aperture selection with Canon EF version. Dimensions: 25 x 76 x 72mm for Canon EF version Weight: 161 grams for Canon EF version Tripod Mount: Robust removable type with Arca Swiss compatibility