The movie cameras transported 35mm film through the cameras vertically, with an image frame of 18x24mm. In 1913, Oskar Barnack, an engineer at Leitz, designed a prototype still camera that transported the film horizontally, producing a 24x36mm image frame. By 1925, the Leica I was introduced and became a commercial success. In time, the 24x36mm format became one of the most produced and used image formats in all of photography. This still holds true in digital cameras today.