Lens adapter manufacturer Metabones has launched a pair of long-awaited Canon EF to Micro Four Thirds lens adapters. The first adapter is the Smart Mount version which allows electronic control of the aperture in a Canon lens from a Micro Four Thirds camera, as well as correct recording of EXIF information and activation of Image Stabilization where present. 

The second adapter is the Canon EF to Micro Four Thirds Speed Booster which has all the features of the Smart Adapter, but also includes an optical element to add further benefits.

Just like the other available Speed Boosters from Metabones, the Canon EF to Micro Four Thirds version makes effective focal length 0.71x wider, increases maximum aperture by one stop and, in theory, even increases sharpness compared with using the regular Smart Adapter.

When used on a Micro Four Thirds camera, it effectively lowers the camera's 'crop factor' from 2x to 1.42x. This means it gives a slightly wider angle-of-view than an APS-C camera would, for any given focal length. This is good for videographers, since that means lenses will behave very much as they do on the common 'Super 35' format (which is essentially APS-C sized). The adapter works exclusively with full EF lenses, since EF-S lenses, designed for the APS-C format, are likely to produce vignetting.

See the new Speed Booster in action with the Panasonic GH4 in the sample video below.

Video courtesy of EOSHD

If you want to read a little bit more about the physics behind the Speed Booster, optical designers Brian Caldwell and Wilfried Bittner have a white paper available on the Metabones website. You can also take a look at our hands-on with the Canon EF to Sony NEX Speed Booster

Whilst the 4K capable Panasonic Lumix DMC-GH4 is listed as a likely candidate to partner with these adapters (we discuss more about the advantages of this pairing in our in-progress Panasonic GH4 review), they'll also work with any other camera that has an active Micro Four Thirds mount.

When you consider the growing number of cameras with this mount, as well as the number of third party manufacturers also making lenses with an EF mount, the range of possibilities is almost endless. Since Canon's own entry into the mirrorless market was somewhat lackluster with the EOS M, this also gives Canon users another opportunity to own a smaller camera that can still make use of their current lens collection.

It's worth noting that for now, autofocus is listed as unsupported by either of these adapters. Some models of Metabones adapters do support autofocus, such as the Canon EF to Sony NEX Smart Adapter, albeit in a limited fashion. Exact shipping dates have yet to be confirmed but the Canon EF to Micro Four Thirds Smart Adapter will cost $399, while the Canon EF to Micro Four Thirds Speed Booster will cost $599 from www.metabones.com.