Viltrox EF-Z2 Canon EF Lens to Nikon Z Mount 0.71x Speed Booster with AutofocusViltrox EF Z2 Canon EF Lens to Nikon Z Mount 0. 71x Speed Booster with Autofocus Viltrox EF Z2 speed booster allows your Nikon Z6,Z7 or Z 50 to have more lens options among EF mount series, keeping the lens native AF, stabilization performance as well as supports Nikon's Face and Eye Detection AF. It also features 0. 71x equivalent focal length based on the original focal length and increase your camera's aperture by 1 stop.