Tokyo Kogaku Topcor S 5cm f/2 Type 1

Tokyo Kogaku Topcor S 5cm f/2 Type 1

Among the Japanese normal lenses of the screw-mount era, the chrome Topcor S 5cm f/2 has a strong reputation, with collectors and users often ranking it as one of the better M39 standard lenses of the pre-Summicron period [1]. It was made by Tokyo Optical Company (Tokyo Kogaku), the firm behind the later Topcon system, which was established in 1932 and began producing lenses in 1935; after the war the company built a line of LTM lenses that carried the names State, Simlar and C.Simlar before the Topcor brand was adopted [1]. The 5cm f/2 was supplied with the Leotax family of rangefinders rather than being sold widely on its own, which shapes both its history and its scarcity today [1].

The lens uses a six-element, four-group optical design, a double-Gauss arrangement described in reviews of the related Topcor 50mm lenses as based on a Biotar layout [2]. It is built in chrome with a heavy, well-machined barrel typical of quality 1950s primes, focuses to one metre, and uses a ten-blade diaphragm with click stops down to a minimum aperture of f/16 [1]. The barrel does not couple to the rangefinder mechanism, so focus is set on the lens scale, and the screw mount fits standard LTM (M39) bodies. Users report smooth focusing without play and consistent, evenly spaced aperture detents, and rate its handling on a par with contemporary Nikkor and Canon screw-mount lenses [1].

The f/2 normal lens went through several closely related forms within a short span. A chrome Topcor 5cm f/2 without the "S" suffix appeared first on Leotax bodies, and was followed by the chrome Topcor S f/2 covered here, with later black-and-chrome "panda" and black aluminium barrel variants also documented; all of these share the six-element, four-group formula and ten-blade diaphragm [1]. The Topcor lenses were offered across several Leotax models over roughly 1956 to 1961, after which a later black Topcor S 5cm f/1.8 of similar construction took over as the kit lens, distinguished by visibly different front elements [1].

Optical qualities

Rendering Documented impressions of the chrome Topcor S 5cm f/2 are largely from collector and user accounts rather than formal testing. These describe it as sharp, with rendering that several long-term owners compare favourably to 1950s and 1960s Summicrons, and report backgrounds that are less harsh or "edgy" than some rivals of the period [1]. One user noted that, in side-by-side use, a modern aspherical Summicron was slightly contrastier and marginally sharper only at the widest apertures, while the Topcor's results were consistently pleasing [1]. These are subjective observations and should be treated as user consensus rather than measured performance.

History

Development and Launch Tokyo Kogaku entered postwar LTM lens production after building larger-format and military optics, evolving its branding from State and Simlar to Topcor [1]. The 5cm f/2 was developed as a fast standard lens for the Leotax rangefinder line and was bundled with those cameras rather than marketed as a stand-alone optic, with the chrome f/2 appearing in the mid-1950s and the Topcor S version following shortly after [1].

Production Evolution The normal f/2 line moved quickly from an early chrome Topcor 5cm f/2 to the chrome Topcor S, then to black-and-chrome "panda" and black aluminium-barrel versions, all retaining the six-element, four-group design and ten-blade diaphragm [1]. The Topcor S 5cm f/1.8 that succeeded the f/2 on the Leotax G shared much of the construction but used different front elements [1].

Collector Notes Production numbers for the 5cm f/2 are not clearly recorded, and the lens is considered uncommon today; many examples survive attached to Leotax bodies, where they tend to be inexpensive, while clean lenses sold separately command higher prices [1]. Buyers should check the optics for haze and confirm the smooth, even focus and click stops that owners associate with good examples [1]. One discrepancy worth noting: this lens's filter thread is recorded by LeicaLensList as 41 mm, while at least one collector source lists 40.5 mm for the Topcor 5cm f/2, so the accessory thread is worth verifying on the specific example before buying filters or a hood [1].

Sources

• [1] Leicaphilia. The Leica Thread Mount Topcor 50 f/2. https://leicaphilia.com/the-leica-thread-mount-topcor-50-f-2/
• [2] 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/