Firmware update for EF to EFM /RF(EOS R) Speed Booster ULTRA (Windows)

Firmware upgrade for Canon EF - EF-M(EOS M) and EF - RF(EOS R) T Speed Booster ULTRA^®

RELEVANT PRODUCTS

This information is for the following models:

• Canon EF to EF-M (EOSM) T Speed Booster® ULTRA 0.71x (MB_SPEF-EFM-BT1)

• Canon EF to RF (EOS R) T Speed Booster® ULTRA 0.71x (MB_SPEF-EFR-BT1)

• Canon EF to RF (EOS R) T Speed Booster® ULTRA 0.71x CINE (MB_SPEF-EFR-BT2)

Disclaimer: these release notes only highlights significant changes to the firmware. There may have been other changes that are not documented.

ABOUT THIS DOWNLOAD

• Name: Firmware update V2.50 (#2124) for Canon EF to RF (EOS R) T Speed Booster® ULTRA
• Release date:  22 Dec 2025
• Benefits and improvements: 
  • Fixed unresponsive autofocus issue with Tamron 35-150mm F/2.8-4 VC USD model A043 on EOS C70 firmware v1.1.1.1. Note that this fix is exclusive to Metabones EF-RF Speed Boosters and the hang issue may still occur with other adapters.
  • Fixed issue when Canon EF-S 18-135mm f/3.5-5.6 IS USM a.k.a. "NANO USM" is used with Power Zoom Adapter PZ-E1, the green LED of the PZ-E1 does not go off while the camera is turned off. Metabones Speed Booster reports itself as a cropped APS-C lens.
  • By default, Metabones Speed Booster reports itself as a cropped APS-C lens. This was not consistent in previous versions but only with newer lenses. This is now fixed and consistent across the board. This behaviour can be disabled by a setting in Metabones App.

• Name: Firmware update V1.40 (#1924) for Canon EF to EF-M (EOS M) T Speed Booster® ULTRA
• Release date:  30 Jun 2025
• Benefits and improvements: 
  • Fixed issue when Canon EF-S 18-135mm f/3.5-5.6 IS USM a.k.a. "NANO USM" is used with Power Zoom Adapter PZ-E1, the green LED of the PZ-E1 does not go off while the camera is turned off. (EF-S lenses require modification to fit Speed Booster and some do not fit at all.)

FIRMWARE HISTORY: 

• More firmware history can be viewed in the archive: here

SYSTEM REQUIREMENTS:

Operating Systems

The latest version of the firmware update is compatible with most commonly-used versions of Microsoft Windows:

• Windows® 10 1809 or newer (64-bit)
• Windows® 11

A micro-USB cable is required to connect the Smart Adapter^TM or Speed Booster® to the computer.

While performing the firmware update, don't disconnect the USB cable, otherwise, the adapter may become inoperable due to sudden disconnection. In most cases, an adapter made inoperable by an interrupted firmware update can be fixed by performing the firmware update again.

Don't connect the adapter to any camara or lens while performing the firmware update.