Leotax rangefinders produced by Showa optical co, with Simlar and Topcor LSM lenses, and some separate Topcor screwmount lenses (39mm) (1949-1958).

Showa optical co. started just before WWII with making of Leica copies. After the war the production restarted. Around 1948 with the appearance of the Leotax DII all Leotax rangefinder were mounted with standard lenses produced by Tokyo Kokagu. The Leotax Leica copies remained popular until the present day, they have a special handmade special quality about them often surprising the true Leica devotee. Next to US armyshop sales in Japan, Leotax camera were exported to the US and Europe.

With the spread of the Leotax the quality of Tokyo Kogaku Simlar and Topcor lens series became wider known. The optical design of some these screw mount lenses were continued in the R Topcon (the 9 and 13,5 cm) , F auto Topcor (13,5 cm) and Re-Topcor series (early 13,5 cm). Strangely the special Simlar and Topcor 5cm 1:1,5 ridged lens did not reappear. Although very hard to prove the Leonon 5 cm lens mounted on the Leotax Elite seen in all aspects very close to the Topcor-S 5cm.

The Showa company was founded in January 1938 by Nakagawa Kenzō as Kyōei-sha, based in Nippori, Tokyo.Nakagawa, a former engineer of Konishiroku, obtained financial support from Minagawa Shōten. The company was renamed G.K. Shōwa Kōgaku at the end of 1938. The company’s most emblematic product was the Leotax, a Leica-style 35mm camera, initially made with an uncoupled rangefinder. However during the early years, the company’s main activity was the production of the more pedestrian Semi Leotax 4.5×6cm folding camera. The company became Shōwa Kōgaku Seiki K.K. at some point, certainly after World War II. The Leotax camera switched to a coupled rangefinder in 1947 since German pre-war patents were declared invalid by the USA. Together with the Nicca and the Canon II/III/IV, the camera was one of the main Japanese Leica copies, gradually improved until the late 1950s. The company was also making improved Semi Leotax models, as well as the Gemflex subminiature TLR. The company was renamed Leotax Camera K.K. in 1956 or 1957. It made rangefinder cameras until 1961, the last model being the Leotax G, an advanced camera inspired by the Leica M3.