Founded by Ernst Leitz in 1924. The name Leica is derived from the first three letters of his surname (Leitz) and the first two of the word camera: lei-ca.
The first 35mm film Leica prototypes were built by Oskar Barnack at Ernst Leitz Optische Werke, Wetzlar, in 1913. Intended as a compact camera for landscape photography, particularly during mountain hikes, the Leica was the first practical 35 mm camera that used standard cinema 35 mm film. The Leica transports the film horizontally, extending the frame size to 24×36mm with a 2:3 aspect ratio, instead of the 18×24 mm of cinema cameras which transport the film vertically.
The Leica had several model iterations, and in 1923 Barnack convinced his boss, Ernst Leitz II, to make a pre-production series of 31 cameras for the factory and outside photographers to test. Though the prototypes received a mixed reception, Ernst Leitz decided in 1924 to produce the camera. It was an immediate success when introduced at the 1925 Leipzig Spring Fair as the Leica I (for Leitz camera). The focal plane shutter has a range from 1/20 to 1/500 second, in addition to a Z for Zeit (time) position.
Barnack conceived the Leica as a small camera that produced a small negative. To make large photos by enlargement, (the "small negative, large picture" concept) requires that the camera have high quality lenses that could create well-defined negatives. Barnack tried a Zeiss Tessar on his early prototype camera, but because the Tessar was designed for the 18×24 mm cine format, it inadequately covered the Leica's 24×36mm negative. Barnack resorted to a Leitz Summar lens for the prototype, but to achieve resolution necessary for satisfactory enlargement, the 24x36 mm format needed a lens designed specially for it. The first Leica lens was a 50 mm f/3.5 design based on the Cooke triplet of 1893, adapted by Max Berek at Leitz. The lens has five elements in three groups—the third group being three cemented elements—and was initially named the Leitz Anastigmat. Unlike other triplets, the Leitz Anastigmat has the diaphragm between the first and second elements. When the Leica was first vended, this lens was renamed the ELMAX, for Ernst Leitz and MAX Berek. By 1925, the Leitz laboratories had produced glasses with improved optical properties, and Professor Berek designed an improved version of the ELMAX named the ELMAR that had four elements in three groups. The third group was simplified to two cemented elements, which was easier and cheaper to make. Professor Berek had two dogs, Hektor and Rex. The first of these, Hektor, gave his name to a series of Leica lenses, and the name of the second appeared in the SummaREX.