nomad wrote:The position is not the same.
MFT has a very short flange distance, while EF is taking the swinging mirror into account.
The distance will be the same and there is no swinging mirror on a bmcc. The lens has to be a set distance from the sensor or it will not function. The ef mount has a longer flange distance to accommodate the mirror on a dslr, but it is just a convenient mount choice to use on the bmcc. If you purchase an ef -> mft adapter it is basically a tube which ensures that the lens is the correct distance from the sensor (i.e. the same distance regardless of whether it is a native ef mount, or an ef -> mft adapter on and mft mount). The same is true if you are adapting another lens to ef or mft, for example:
(ef flange distance + c/y -> ef adapter) = (mft flange distance + c/y -> mft adapter)
The reason why mft is good for adapting other lenses to is because it is relatively easy to construct an adapter to position a lens further away from the sensor. Whereas it is difficult, detrimental (e.g. using lenses in the adapter), or impossible to recess a lens into the mount of the camera.