Metabones Speed Booster ULTRA 0.71x for X-mount cameras Always Enhance and Never Degrade the Performance of the Attached Master Lens. Sharper corners, less distortion, reduced vignetting New optical design: 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. Like the revolutionary original Metabones Speed Booster announced in January 2013, the Speed Booster ULTRA has a magnification of 0.71x, and so it effectively reduces the crop factor of mirrorless cameras with DX-sized sensors and Super35 camcorder, such as Sony E-mount, Fuji X-mount cameras Sony FS7 MARKII, from 1.5x to 1.07x. However, the new ULTRA design makes very effective use of exotic materials at the furthest limit of glassmaking technology, and as a result is well corrected for use with virtually all full-frame SLR/Prime lenses regardless of exit pupil distance. Why Metabones? Since its inception, Metabones has been designing and manufacturing lens adapters recognized among professionals and enthusiasts as leaders in design and workmanship. The lens side of the adapter features a strong leaf-spring structure, strengthening the adapter-lens connection and ensuring tightness of the lens in order to reduce wear and prevent focus errors and optical alignment issues from appearing. Metabones uses matte-black treatment to keep internal reflection to a minimum in order to maintain the maximum optical quality possible with the lens. All Metabones Adapters follow this tradition of uncompromising precision, robust build quality and outstanding finish. Our new Smart Adapter series of products add industry-leading electronic interfacing technology from Canada, with true electronic control of the lens' aperture directly from the camera body.