The Speed Booster Ultra from Metabones allows a full-frame or APS-C Nikon G F-mount lens to be mounted onto a Micro Four Thirds compact system camera. Like the previous Metabones Speed Booster model, the updated Ultra has a magnification of 0.71x so it effectively reduces the crop factor of mirrorless cameras with DX-sized sensors, such as Sony E-mount and Fuji X-mount cameras, from 1.5x to 1.07x. However, the new optical design in the Ultra uses advanced 5-element/4-group optical design incorporating ultra-high index tantalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion and reduced vignetting.