The Metabones BMPCC4K Speed Booster XL 0.64x F-Mount to MFT-Mount Lens Adapter mounts F-Mount lenses on an MFT-Mount camera body. Its optical group compresses the image circle to 0.64x, which widens the field of view and adds one and a third stops of light. An aperture ring on the adapter sets the diaphragm, which keeps a lens with no aperture ring of its own controllable. A tripod foot carries the weight of the lens instead of hanging it off the camera mount.