The Blackmagic Design Cinema Camera introduced at NAB came with a Canon EF mount–which was great if you had Canon EF still lenses. You may have been less thrilled if your inventory of lenses consisted of PL, or any of the other still lens brands on the planet.
Blackmagic has a companion model at IBC–same body, but with a Micro Four Thirds lens (MFT) mount. MFT has a flange focal depth of 19.25 mm (compared with Canon EF depth of 44 mm). This short flange depth is almost a neutral mount–since there are so many adapters on the market. You can attach almost anything.
The new mount is mechanical — there aren’t any contacts. It is easily identified by its much shorter profile. Remember–there is a crop factor. The Blackmagic sensor is about 15.9 x 8.8 mm.