Although there were cameras that took 35mm film before 1925, it was the Leica, introduced that year, which popularised 35mm as a film for still, rather than movie, photography and made the format truly viable. The Leica was the brainchild of Oskar Barnack who joined the Leitz company originally to develop a top-quality cine camera. But, following a series of twists and turns, he ended up designing a still camera for 35mm cine film. In the cine world, 35mm ran through the camera and projector vertically with a frame size of 24x18mm. For his camera, Barnack turned the film sideways, ran it through the body horizontally and doubled one dimension of the cine image, expanding it from 24x18mm to 24x36mm. Thus the standard 35mm frame size was established. It was a size that ruled the majority of 35mm cameras, be they viewfinder, coupled rangefinder (CRF), single lens reflex (SLR) or even twin lens reflex (TLR) models from then until the digital age. Because 35mm is still readily available, all these cameras are still usable today. But beware. Not every maker stuck to the 24x36mm format rule.
Slightly smaller formats
In 1951 Nikon used a 24x32mm format for its first 35mm coupled rangefinder camera, upped it to 24x34mm with the next model and only adopted the 24x36mm standard with its third camera. When the Wray Optical Company made the first Wrayflex, also in 1951, the format was 24x32mm but that was upgraded to 24x36mm two years later. One reason
