EF to Micro 4/3 Speedbooster Metabones

This Speed Booster version optically reduces the lenses image circle so that the field of view is the same as it would be on a full frame 35mm stills chip camera. EG: a 25mm lens will have the same field of view on a GH4 as it would on a Canon 5D using this adaptor. The  optical quality of the speed boosters  is surprisingly good  and they preserve most of the electronic functionality of the recent  Canon lenses (including stabilisation if  available) It also increases the lenses speed by 1 stop, hence the name.