Tokyo Kogaku Topcor 135mm f/3.5

Tokyo Kogaku Topcor 135mm f/3.5

Among the Leica screw-mount lenses produced by Tokyo Kogaku (Tokyo Optical Company), the Topcor 135mm f/3.5 is one of the less common entries, a medium telephoto made for the company's Leotax-compatible rangefinder line rather than for its later Topcon single-lens reflex cameras. Tokyo Kogaku was established in Tokyo in 1932 and began making lenses in 1935, at first concentrating on larger-format optics and lenses for the Japanese military before moving into Leica Thread Mount lenses for Leotax cameras after the war [1][2]. These screw-mount optics were first branded "State," then "Simlar" and "C.Simlar," before the "Topcor" name was adopted [1]. The 135mm sits at the long end of that screw-mount family, alongside the better-known 50mm and 35mm Topcors.

The lens uses a four-element optical design in three groups and carries a 46mm filter thread. It focuses to about 1.52 m at its closest setting, which is typical for a telephoto of this length and era. Tokyo Kogaku's screw-mount lenses were regarded as fine optics in their day, with build quality on a par with 1950s Leica Thread Mount lenses from Japan and Germany [1]. The 135mm mounts on M39 screw bodies and, with a simple adapter, on Leica M cameras. As with all 135mm rangefinder lenses, a focal-length-appropriate finder is helpful because many rangefinder viewfinders do not show 135mm framelines; period 135mm Topcor lenses were sometimes supplied with an accessory multi-frame finder. Whether this particular lens is mechanically coupled to the camera rangefinder is not confirmed.

Documentation of the screw-mount 135mm Topcor is thin, and surviving examples are scarce, which makes firm statements about variants, finishes, and production figures difficult. It should not be confused with Tokyo Kogaku's later reflex telephotos, including the R. Topcor and RE Auto-Topcor 135mm lenses made in the Topcon (Exakta-derived) bayonet mount for the Topcon R and RE Super single-lens reflex systems, which are far more frequently encountered.

Optical qualities

Rendering Reliable, independently verified rendering data for the screw-mount Topcor 135mm f/3.5 is limited because so few examples are documented. As a four-element telephoto from the 1950s, it can be expected to behave like other modest-aperture rangefinder long lenses of the period, but specific, well-supported claims about its sharpness, contrast, bokeh, flare, distortion, or digital performance are not available from sources that could be confirmed here. Tokyo Kogaku's screw-mount optics in general were considered sharp and well made for their time [1].

History

Development and Launch Tokyo Kogaku Kikai K.K. (Tokyo Optical Company, Ltd.) was founded in 1932 and started making lenses in 1935 [1]. Its earliest products were three- and four-element designs sold under names such as State, Toko, and Simlar, and like Nippon Kogaku (later Nikon) the firm was a major supplier of optics to the Japanese military before 1945 [2]. After the Second World War the company expanded into Leica Thread Mount lenses for Leotax cameras, a Japanese rangefinder line built in the Leica idiom [1][2]. The Topcor 135mm f/3.5 belongs to this postwar screw-mount group, which was progressively rebranded from State and Simlar to Topcor as the company consolidated its lens naming [1].

Special editions No major factory special editions or military variants of the screw-mount Topcor 135mm f/3.5 are widely documented.

Collector Notes Buyers should be careful to distinguish the Leica screw-mount Topcor 135mm f/3.5 from the company's later reflex 135mm lenses, the R. Topcor and RE Auto-Topcor, which were made for Topcon single-lens reflex cameras in a bayonet mount and are much more common [2]. As with any vintage Japanese telephoto, internal haze, cleaning marks, and coating condition are worth checking, since these affect contrast more than minor external wear. Because the screw-mount 135mm is uncommon and lightly documented, originality of mount and barrel is best confirmed in person; some Topcor lenses have been converted to other mounts by later owners. A suitable 135mm accessory finder is useful for framing on cameras that lack 135mm framelines.

Sources

• [1] Leicaphilia. The Leica Thread Mount Topcor 50 f/2. https://leicaphilia.com/the-leica-thread-mount-topcor-50-f-2/
• [2] Mike Eckman. Topcon R (1957). https://mikeeckman.com/2021/12/topcon-r-1957/