New optical design: advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion and reduced vignetting.

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, such as Sony E-mount and Fuji X-mount cameras, from 1.5x to 1.07x.

• Increase maximum aperture by 1 stop.
• Increase MTF.
• Makes lens 0.71x wider.
• Advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass by Caldwell Photographic in the USA (patent pending).
• Electronic integration of aperture diaphragm, controlled by or from the camera body.
• Partial autofocus support for late-model (post-2006) Canon-brand lenses.
• Powered by camera body. No external power source required.
• High performance 32-bit processor and efficient switched-mode power supply.
• The tripod foot is detachable and compatible with Arca Swiss, Markins, Photo Clam ball heads.