One of the rarest of all Leica accessories and described by Hasbroeck as 'by far the most original and effective contribution of Leitz's towards stereo photography'. As early as 1926 Leitz were manufacturing accessories to allow Leica camera users to make stereo pairs, firstly by physically moving the camera along a fixed bar (the FIATE) and secondly by the attaching a stereo prism (the Stereoly) to the front of the camera's standard lens. Further ideas involved developing a stereo camera, whih never entered production, and by pairing cameras on to a special mounting bar. These methods all had their drawbacks.
Wilhelm Albert, the successor to Oskar Barnack as chief designer at Leitz, between 1937 and 1942 designed paired lenses held in a common focusing mount. These produced a pair of images 24 x 18mm., within the standard 24 x 36mm. format. This became the OWENO for the Elmar and the OVUTO for the Stemar lens, they were probably issued in the early 1940s. A single scale controlled the two diaphragms and focusing was by a single lever. The VIDOM finder was adapted to provide 18 x 24mm. masking and parallax correction was provide an arm coupling to the lens focusing mount.
Production was very limited and certainly fewer than one hundred examples in two serial number batches for both the Elmar and Stemar versions. Hasbroeck and Lager both quote different serial number ranges: 541,053-541,098/567,050-567,081 and 541,051-541,000/567,051-567,100, respectively.
With the main lens was the variable separation prism OTEMO which was produced with a seial number range from 5001-5050, although Laney suggests that only twenty units were actually produced.
All stereo production was stopped shortly after commencing and it was not until 1954 that the Stemar was re-introduced as a 3.3mm. lens.