Oskar Barnack was a precision mechanic and designer at the optical firm Leitz in Wetzlar. His idea was to use 35-millimeter cinema film in a still camera. In 1913 and 1914 he completed the first Leica camera and two prototypes.
According to the Leica magazine LFI, it seems plausible that his asthma and his passion for nature photography led him to the idea. The magazine adds that none of the stories about the camera’s origin can be confirmed with certainty.