Metabones Speed Booster Ultra 0.71x Adapter for Canon Lens to Micro Four Camera

Optical
Increase maximum aperture by 1 stop
Increase MTF of any lens attached
Makes lens 0.71x wider
Patented 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass by Caldwell Photographic in the USA

Electronic
Auto focus on Panasonic Mirco Four Thirds cameras
Can be powered either by camera body or by third-party external 5V power source (not included)
Iris/aperture controlled by the camera body
Image stabilization (IS) lens support
Electronic manual focusing (e.g. EF 85/1.2L II and discontinued EF 50/1.0L)
EXIF (focal length, aperture, zoom range)
Distance and zoom display on camcorders (requires lenses supporting distance information)

Other
Detachable tripod foot compatible with Arca Swiss, Markins and Photo Clam ball heads
Flocking material coating to reduce the internal reflection

Limitations
EF-S lenses require modification to fit (but third party DX lenses can be used without modification)
No autofocus support for JVC and Olympus
AFC (continuous AF) and AFF (flexible AF) modes are not supported
No 24p video AF
Video AF may hunt more than a native lens
No support for in-camera correction such as peripheral shading, CA and distortion
Designed to cover an 17.3mm x 13mm sensor but not enough to cover Super35 so JVC GY-LS300 needs to have VSM configured to 80%

Always Enhance and Never Degrade the Performance of the Attached Master Lens
Like the ULTRA series for Sony E-mount, the new Speed Booster ULTRA m43 uses an advanced 5-element 4-group optical design incorporating ultra-high index tantalum-based optical glass. However, the new design is specifically optimized for the Micro Four Thirds sensor and filter stack and as a result achieves an astonishing level of performance that sets a new standard for focal reducers.

Like the revolutionary original Metabones Speed Booster announced in January 2013, the Speed Booster ULTRA m43 has a magnification of 0.71x and so it effectively reduces the crop factor of mirrorless Micro Four Thirds mount cameras from 2.0x to 1.4x. However, the new ULTRA design makes very effective use of exotic materials at the furthest limit of glassmaking technology and as a result is almost perfectly corrected for use with all fullframe SLR lenses regardless of aperture. The Speed Booster ULTRA m43 will also work extremely well with many DX and APS-C format lenses provided the image circle of the lens is large enough. Optical performance of the new Speed Boosters is so good that the MTF of any lens attached to it will be improved. Even the latest generation of ultra-high performance SLR lenses such as the Zeiss Otus series can be improved by adding a Speed Booster ULTRA m43. (More information can be found in the press release here and whitepaper here)

Autofocus with an Optimum Balance of Accuracy, Speed, Consistency and Reliability
New in Speed Booster ULTRA for Canon EF Mount to Micro Four Thirds is autofocus on Panasonic camera bodies, subject to certain limitations (see table above for details). They are pleased to report that Panasonic Micro Four Thirds camera bodies are capable of autofocusing accurately even if the maximum aperture of the Speed Booster and the lens combined is in the sub-f/1.0 range. Although Metabones first and foremost priority is accuracy, They are able to make great strides in autofocus speed as well, which is significantly faster than a DSLR Four Thirds lens on a Panasonic Micro Four Thirds camera (with adapter) or their E-mount offerings on Sony cameras prior to Alpha 7R II.

Autofocus Lens Compatibility List
Accurate
Canon EF20-35mm f/3.5-4.5 USM
Canon EF24-105mm f/4L IS USM
Canon EF35-80mm f/4-5.6
Canon EF40mm f/2.8 STM
Canon EF50mm f/1.2L USM