Metabones MB_SPEF-M43-BT3 lens adapter

The Metabones MB_SPEF-M43-BT3 lens adapter enables the use of Canon EF lenses on Micro Four Thirds camera bodies while preserving electronic communication between lens and camera. Constructed in a black and silver finish, this adapter is designed to provide a stable mechanical connection and to support autofocus and aperture control where the lens and camera combination allow. The adapter incorporates an optical Speed Booster XL 0.64x design that has been reworked for Micro Four Thirds systems, increasing working distance and optimizing optical spacing for the thicker filter stack commonly found on MFT cameras.

Advantages

This adapter increases compatibility between Canon EF glass and Micro Four Thirds bodies while maintaining electronic lens functions such as autofocus and aperture control where supported. The redesigned Speed Booster XL 0.64x optics produce a reduced crop factor and a wider effective field of view compared with an unmodified mount, while optical optimization for a 4 mm filter stack and an increased image circle ensure coverage of the Four Thirds imaging area. An increased working distance reduces the risk of contact with shutter or outer covers on certain camera models.

Suitable for

• Photographers who want to use Canon EF lenses on Micro Four Thirds cameras
• Videographers seeking a wider effective field of view using Speed Booster optics
• Users of Panasonic GH4 and other MFT cameras that require increased working distance
• Those needing preserved electronic communication for autofocus and aperture control

Key specifications

• Mount conversion: Canon EF to Micro Four Thirds
• Optical type: Speed Booster XL 0.64x design for reduced crop factor
• Optimized filter stack thickness: designed for 4 mm Micro Four Thirds filter stack
• Increased working distance: +1 mm compared with previous Blackmagic-specific design
• Image circle diameter: enlarged to cover Four Thirds format (approximately 21.63 mm)
• Finish: black and silver
• Maintains electronic communication for autofocus and aperture control where supported

How to use

Attach the adapter to the Micro Four Thirds camera body by aligning the mount marks and turning until it locks in place. Mount the Canon EF lens onto the adapter in the same manner, ensuring secure engagement. Power on the camera and verify lens communication; the camera should recognize the attached lens and enable supported electronic functions such as autofocus and aperture control. When using the Speed Booster XL 0.64x functionality, check framing and focus as the effective focal length and depth of field will change compared with native MFT lenses.

Recommendations

For reliable operation, confirm lens and camera firmware compatibility and test autofocus and aperture control with your specific lens models. When using on Panasonic GH4 and similar bodies, the increased working distance and optimized optical spacing reduce the risk of physical contact with shutter covers; still, exercise care when mounting and dismounting lenses. For critical imaging, evaluate corners and coverage in your camera’s resolution modes, especially when shooting Cinema 4K on compatible bodies.