Tokyo Kogaku Topcor S 5cm f/2 Type 2

Tokyo Kogaku Topcor S 5cm f/2 Type 2

Tokyo Kogaku, the optical firm later known as Topcon, earned a strong reputation for its screw-mount rangefinder lenses, which were made in only modest numbers and are now uncommon on the used market [1]. The Topcor S 5cm f/2 belongs to this small family of Leica-thread-mount fifties, and the Type 2 is the later production variant of that lens. It uses a double-Gauss, Planar-type optical arrangement of six elements in four groups, in the classic 1-2-2-1 layout shared with designs such as the Biotar, Helios and Xenon [2]. Collectors value it both as a scarce piece of Japanese rangefinder history and for a rendering that combines high sharpness with a distinctive out-of-focus character.

The lens is a compact, all-metal standard prime with a ten-blade diaphragm and a 41 mm filter thread, focusing to one meter. Like the other Topcor screw-mount fifties it is not rangefinder coupled in the modern sense expected of native Leica optics, and handling has been compared to the later Canon Leica-thread lenses: solid and pleasant rather than overbuilt, with a focusing lever and no infinity lock [1]. The minimum aperture is f/16 with click stops [1]. Build quality is generally regarded as good, and the barrel of the later black version has the look and feel of a conventional modern fast prime [1].

Two finishes of the 5cm f/2 are documented: an earlier chrome version and a later black version, which differ in the placement and design of their controls and are therefore likely different internally as well [1]. The lens was supplied with the Leotax series of rangefinder cameras from roughly 1954 to 1961, appearing as an option on bodies including the F, T, K, FV, TV2 and T 2L according to the reference work Leica Copies by HPR [1]. Whether the Topcor screw-mount lenses were also sold separately is not clearly documented [1].

Optical qualities

Rendering Documented impressions describe the lens as sharp and well corrected for a 1950s design, consistent with Tokyo Optical's reputation for capable optics [1][3]. The double-Gauss formula is associated with a pronounced swirly bokeh, while the lens itself is reported to be sharp [2]. Detailed, systematic test data is limited, so finer points of contrast, flare and field behavior are not well established in published sources.

History

Development and Launch Tokyo Kogaku (Tokyo Optical Co., later Topcon) produced its Leica-thread-mount lenses during an era when its optics were already held in high regard, and the screw-mount examples were made in comparatively small quantities [1][3]. The 5cm f/2 Topcor was offered as a standard lens for the Leotax rangefinder cameras from about 1954 until about 1961 [1].

Production Evolution Over its production life the 5cm f/2 appeared in two distinct forms. Earlier Leotax F and T bodies are shown in HPR's reference carrying a chrome-finished 5cm f/2, while later cameras came with a black-finished version [1]. The two are not merely cosmetic variants: they differ in the layout and design of their controls, suggesting internal differences as well, though the extent of those differences is not documented [1].

Special editions The closely related Topcor S 50mm f/1.8 exists in a rarer two-tone "Panda" form, but no widely documented factory special editions of the 5cm f/2 itself are recorded beyond the standard chrome and black finishes [1].

Collector Notes The chrome and black 5cm f/2 Topcors surface for sale only occasionally, sometimes attached to Leotax bodies and sometimes on their own, and usually command high prices [1]. Buyers should confirm the lens against the camera it is paired with, since faster and slower Topcor fifties (including the f/1.8 and f/3.5) were offered on the same bodies and can be confused [1]. As with most lenses of this age, haze and iris stiffness are worth checking before purchase [1]. One first-hand owner account measured a seven-element construction and a 40.5 mm filter thread, which differs from the recorded six-element design and 41 mm filter; the verified figures should be treated as authoritative [1].

Sources

• [1] legacycamera. The Topcor-S 5cm F2 for Leica Thread Mount. https://legacycamera.wordpress.com/2012/05/12/the-topcor-s-5cm-f2-for-leica-thread-mount/
• [2] Flickr. Tokyo Kogaku Topcor-S 5cm f2 (tags: Topcor-s). https://www.flickr.com/photos/tags/Topcor-s/
• [3] 35mmc. Tokyo Optical Co. Topcor 50mm f/1.5 LTM (Semi-Sonnar) Mini-Review. https://www.35mmc.com/03/08/2020/tokyo-optical-co-topcor-50mm-f-1-5-ltm-semi-sonnar-mini-review/