The Viltrox EF-E II electronic adapter (F Booster) is the second generation of this type, released at the end of 2014. Like the previous generation, the built-in optics increase light intake by one F-stop and reduce the focal length by 0.71x. Similar to the last EF-NEX IV, the new F Booster also features a USB port for firmware updates and a switch to select the focus mode between CDAF or PDAF. Note: Not compatible with full-frame cameras in the NEX series.