Tokyo Kogaku Topcor S "Panda"

Tokyo Kogaku Topcor S "Panda"

Among Japanese Leica thread-mount normals of the 1950s, the Topcor S 50mm f/2 stands out as much for its two-tone "Panda" livery as for its reputation, with some collectors describing it as the only double-Gauss lens of its type offered in screw mount [1]. It was built by Tokyo Kogaku Kikai K.K. (Tokyo Optical Company), a firm founded in Tokyo in 1932 that began making lenses in 1935, supplied optics to the Japanese military, and turned to Leica thread-mount lenses after the war under the names State, Simlar, C.Simlar and finally Topcor [2]. The "S" in Topcor S has been read as standing for "Special" [1]. The lens reached photographers as the standard optic on the Leotax rangefinder cameras rather than as a separately boxed product, which is one reason clean, body-free examples are uncommon today [2].

The optical design is a six-element, four-group double-Gauss arrangement, and this formula was carried unchanged across the barrel revisions of the f/2 [1][2]. The lens uses a ten-bladed diaphragm and a 40.5 mm filter thread, focuses by a coupled helicoid down to 1 m, and is built to a heavy, all-metal standard that owners frequently compare favourably with contemporary Nikkor, Canon and Leitz screw-mount lenses [1][2]. Handling differs by version: the earlier barrels rotate through a long throw for the full focus range and carry one-third-stop aperture markings, while the later straight barrel has a much shorter throw, a focusing tab, and full-stop click detents, giving quicker operation on a rangefinder body [1]. As a Leica thread-mount lens it mounts on M39 bodies and, via an adapter, on M-mount and mirrorless cameras; it is rangefinder coupled on the screw-mount cameras for which it was made [1].

Several variants are documented. A plain Topcor 5cm f/2 (without the "S") appeared around 1956 with a different six-element, five-group design and should not be confused with the later lens [1]. The Topcor S itself was offered first in full chrome and then in the chrome-and-black "Panda" finish, followed by a black aluminium-barrel version [1][2]. Published accounts of the exact sequence and dating vary, with one collector source placing the chrome Topcor S in 1957, the panda update in 1958 and a black version the same year [2]. A later black Topcor S 5cm f/1.8, introduced with the Leotax G around 1961, shares the same six-element, four-group layout, ten blades and 40.5 mm filter but has visibly different front elements; it is rarer and more costly than the f/2 [1][2].

Optical qualities

Rendering The Topcor S is regularly praised as one of the better pre- and early-Summicron-era 50mm screw-mount lenses, with users rating it at least the equal of period Summicrons in build and image quality [2]. Its rendering combines a relatively modern, high-contrast look with a gentle "swirl" in out-of-focus areas associated with the double-Gauss design, most visible against busy or leafy backgrounds [1].

Sharpness Centre sharpness is usable from f/2 and improves noticeably by f/2.8, becoming excellent by f/4 [1]. A mid-zone dip is reported wide open, so off-centre detail benefits from stopping down, with strong corner results from about f/5.6 onward [1].

Contrast and color Contrast is high even wide open for a lens of its age, and the colour rendering is well regarded; comparisons against a modern aspherical Summicron describe the Topcor as slightly less contrasty but pleasing, with backgrounds that are less harsh [1][2].

Flare resistance The lens is coated and controls flare reasonably for its era, but with the sun just outside the frame it can lose some contrast, and a light source within the frame can produce ghosting [1].

Distortion and vignetting Distortion is described as virtually absent. Vignetting is visible at f/2 and improves markedly by f/2.8 [1].

Aberrations A slight focus shift toward the rear is noted on stopping down to around f/4, worth keeping in mind when focusing wide open on a rangefinder, though it is small enough to rarely cause problems in practice [1].

Digital use On mirrorless cameras with an adapter the lens performs well, and one reviewer reports clean results using an autofocus adapter, with the characteristic swirl and high contrast preserved [1].

History

Development and Launch Tokyo Kogaku, established in 1932 and producing lenses from 1935, moved into Leica thread-mount optics after the Second World War, evolving its branding from State and Simlar to Topcor [2]. The Topcor S 50mm f/2 served as a standard lens for the Leotax line of Barnack-style rangefinders built by another Japanese maker, Leotax, and was sold on bodies such as the F, T, K, FV, TV2 and T-2L from the mid-1950s into the early 1960s rather than as a stand-alone lens [2]. One account links the design lineage to a 44mm f/2 lens used in the fixed-lens Topcon 35-S [1].

Production Evolution Across its life the f/2 retained its six-element, four-group optical formula, ten-blade diaphragm and 40.5 mm filter thread while the barrel changed [1][2]. Early lenses were chrome with a long focus throw and third-stop aperture engravings; the later straight barrel adopted a short focus throw, a focus tab and full-stop clicks for faster handling [1]. The chrome-and-black "Panda" finish and a black aluminium-barrel version followed, with sources differing on precise dates [2].

Special editions No major factory special editions of the Topcor S 50mm f/2 are widely documented beyond the recognised chrome, panda and black-barrel finishes and the related, separately introduced f/1.8 lens [1][2].

Collector Notes Total production numbers are not firmly established and clean examples are scarce, partly because so many lenses remain attached to Leotax bodies [2]. Because the design was reused, the plain non-"S" Topcor 5cm f/2 and the later f/1.8 can be confused with the Topcor S, so checking the engraving and front element layout helps confirm identity [1]. Condition is the main concern: haze can erode the high contrast that distinguishes the lens, and fungus is common in examples stored in humid conditions, so the glass should be inspected carefully before purchase [1]. The two-piece construction, an optical block joined to the focusing block by a rear retaining ring, means a loose optical unit can sometimes be re-tightened rather than treated as a fault [1].

Sources

• [1] spaq.in. Focus On The Negative: Topcor-S 50mm f/2 LTM. https://spaq.in/blog/fotn-topcor-s
• [2] Leicaphilia. The Leica Thread Mount Topcor 50 f/2. https://leicaphilia.com/the-leica-thread-mount-topcor-50-f-2/
• [3] AllPhotoLenses. The Topcor-S 50 mm f/2 Lens. Specs. MTF Charts. User Reviews. https://allphotolenses.com/lenses/item/c_4325.html