The T Speed Booster XL 0.64x Adapter for Full-Frame Canon EF-Mount Lens to Select Micro Four Thirds-Mount Cameras 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 1.3-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 T Speed Booster XL 0.64x Adapter for Full-Frame Canon EF-Mount Lens to Select Micro Four Thirds-Mount Cameras 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 1.3 stops of light for each of the lens's f/stop settings.