After WWII, they needed to find marketable products to produce, and they naturaly turned to making cameras for the lenses they had been producing. The examined the two leading 35mm rangefinder cameras of the day, the Leica and the Contax, and produced a camera with the best features of the two. It had the basic layout of the Contax, with it's body mounted focus wheel and bayonet lens mounts. But it had the more reliable shutter found in the Leica. It had a format that was not standard: 24x32. The designers felt it was better proportionate to 8 x 10, and it conserved film, a precios commodity in Japan at that time. They called it simply, The Nikon. It is now refered to as the Nikon I.
