The idea behind the concept was to develop a completely new system that would fully exploit the possibilities that digital technology offers. At the heart of the idea was an agreement between major manufacturers to set a new standard, which established common design rules for a new camera system. The most important of these are a common lens mount, as well as a common communication protocol between lenses and body ensuring that lenses from different makers will have full functionality and are completely interchangeable. Another standard that is laid down is the image circle diameter defining the diagonal dimension of the image as 22,3mm. Olympus have used an 18x13,5mm CCD developed by Kodak giving an aspect ratio of 4:3, but there is nothing to stop future cameras to use a different aspect ratio, providing that diagonal sizes remain the same. The diagonal dimension of the Four-Thirds System is almost exactly half that of 35mm, providing lens coverage of twice the focal length of a 35mm lens.



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