Metabones Speed Booster – Canon EF to MFT adapter
The Metabones Speed Booster range of adapters does two things.
1. Physically adapt a lens from one manufacturer (eg Canon) to fit on another camera (eg a Panasonic Lumix GH4). For Canon lenses they also have to translate the different lens communication protocols back and forth to each other. So the Canon lens thinks it is talking to a Canon camera, and the GH4 camera thinks it is talking to a Canon lens.
2. Using an extra group of lenses, focus the wider image that the lens was designed for onto the smaller sensor on the camera. In doing this, it gives smaller sensor cameras the same coverage and depth of field that the larger sensor would have. It also increases the amount of light hitting the chip, and so means the lens is effectively faster (hence speed booster). So depending on which model you use, an already fast 1.4 lens can become a superfast F 0.74 lens that allows you to film in candlelight if you wish.
This particular adapter is for Canon lenses to Micro Four Thirds mounts such as the Panasonic GH4. It can also be used on the Blackmagic Pocket Camera, but that has a smaller sensor and there is a speedbooster more tailored to that. The one for the pocket though shouldn’t be used on the GH4.