Hello David Simms, 4/3 also happens to be an open standard, with many adapters available, but is not half frame or 50% of the area of a standard 35mm frame; it's quarter frame. 35mm 1x Full Frame Leica DMR 1.37x 52% (half frame) Nikon DX 1.52x 43% *4/3 System* *2x* *25% (qurter-frame)* Welcome to the list! Miha
