Olympus and Panasonic have introduced the Micro Four Thirds standard for a new type of cameras with exchangeable lenses. These cameras will be more compact than digital SLR cameras and allow you to use different lenses but they won't be SLR cameras because they will lack a real optical viewfinder.
The press release claims the Micro Four Third System standard will allow camera makers to make cameras that are approx. 50% slimmer than digital SLR cameras.
he Micro Four Thirds system uses the same sensor size (18 x 13.5 mm) but allows slimmer cameras by removing the mirror box and optical viewfinder. The new format has three key technical differences: (1) roughly half the flange back distance (distance from mount to the sensor), (2) a smaller diameter lens mount (6 mm smaller) and (3) two additional contact points for lens-to-body communication (now 11 points). Removing the mirror mechanism allows this shorter flange back distance, meaning lenses for the new mount can be considerably smaller than current Four Thirds designs. The format will require framing to be carried out using Live View on either the LCD monitor or an EVF. Existing Four Thirds lenses can be used on Micro Four Thirds cameras using an adapter.