If you have an interest in Leicas, and I do, this may be of interest.
It’s funny how technology develops, the 35mm film format could be considered an accident, existing because of movie film,
Oskar Barnack, who was in charge of research and development at Leitz, decided to investigate using 35 mm cine film for still cameras while attempting to build a compact camera capable of making high-quality enlargements. He built his prototype 35 mm camera (Ur-Leica) around 1913, though further development was delayed for several years by World War I. Leitz test-marketed the design between 1923 and 1924, receiving enough positive feedback that the camera was put into production as the Leica I (for Leitz camera) in 1925. The Leica’s immediate popularity spawned a number of competitors, most notably the Contax (introduced in 1932), and cemented the position of 35 mm as the format of choice for high-end compact cameras.