Sankyo-Kohki Komura 105mm f/3.5

Sankyo-Kohki Komura 105mm f/3.5

The Komura 105mm f/3.5 is one of the lesser known short telephoto lenses made for Leica screw mount cameras by the Japanese maker Sankyo Kohki, the firm behind the Komura brand. It sits among a family of rangefinder Komura telephotos that ran roughly from 80mm to 200mm, where the faster 105mm f/2.8 and f/2 versions are more sought after and the f/3.5 is comparatively obscure [1][2]. Built as a rangefinder-coupled lens in the M39 thread mount, it uses a simple three element, three group optical layout and a generous sixteen blade aperture, and its black barrel with chrome trim reflects the late 1950s and early 1960s style of Japanese screw mount optics.

In the hand the lens is notably solid and on the heavy side for its class, larger and weightier than rivals such as the Canon 100mm f/3.5 [1]. The construction follows a typical Komura pattern in which the optical barrel unscrews from the focusing mount, and the barrel itself separates into sections to give access to the surfaces on either side of the diaphragm [1]. Focusing runs on a helical that some owners find stiff, and the metal used in the focus mount appears slightly softer than on many comparable lenses, which is one reason technicians caution against fully separating the helical during a clean and re-lube [1]. Rangefinder coupling is present, but the coupling sometimes needs careful calibration, and at least one detailed teardown reported that the cam and actual focus did not agree without shimming the adapter [1]. With a 43mm filter thread and the LTM mount, it adapts readily to later Leica M bodies and to mirrorless cameras by way of a screw to M or screw to mirrorless adapter.

Two cosmetic variants are documented, distinguished mainly by the engraving on the beauty ring, one reading Sankyo Kōki Japan and another reading Sankyo Kōki Tokyo, with the barrel finished in black and chrome [3]. Collectors should treat the engraving and finish, rather than any single serial scheme, as the practical identification cues, since detailed production records for these lenses are scarce.

Optical qualities

Rendering Documented impressions of this specific lens are limited and come mainly from individual user reports rather than formal testing. The general view is that it is a usable but modest performer, lower in contrast than expected and soft at full aperture, which suits relaxed portraiture more than critical work [1]. One owner using it on digital Leica bodies found it capable for portraits but in need of added contrast and color saturation in some frames, describing it as a lower contrast lens that earns its place for specific looks [2]. As a group, Komura lenses are more often praised for their fast preset telephotos than for the slower screw mount primes, so expectations for the f/3.5 should be set accordingly [4].

Collector and user notes This is treated as an uncommon lens that is collected for its rarity and brand interest rather than for outright optical excellence, and experienced users have argued it is not worth the high asking prices sometimes seen at auction when sharper alternatives like the Canon 100mm f/3.5 or Nikkor 10.5cm f/2.5 exist [1].

History

Development and Launch Sankyo Kohki traces its origins to 1951, when it was founded as an optical research operation, before reorganizing into Sankyo Kohki Co., Ltd. in 1955 [3]. The Komura brand name was coined from characters drawn from the names of company president Mitsuru Kojima and a managing director named Inamura, and US trademark filings indicate the Komura name was first used in 1953 [3][4]. Before settling on Komura, the company had used the Chibanon name on earlier products. Through the 1950s and 1960s the firm grew into one of the larger Japanese third party lens makers, supplying optics in many mounts including Leica thread, Contax, and Exakta, with the Leica screw mount telephotos such as this 105mm forming part of that rangefinder era output [3].

Production Evolution Many Komura interchangeable lenses used a preset diaphragm design in which the front section carried the optical system and aperture while the rear carried the focusing helicoid, and the two could be unscrewed and swapped by hand [3]. The rangefinder 105mm follows this modular construction approach, with the optics module screwing into the focus mount [1]. Over its life the company evolved well beyond rangefinder primes, later building SLR lenses, medium format optics for systems such as Bronica, enlarging lenses, and the Telemore teleconverters, before changing its name to Komura Lens Manufacturing Ltd. around the end of the 1960s and going bankrupt in 1980 [3][4].

Special editions No major factory special editions of the 105mm f/3.5 are widely documented. The lens is mainly encountered in its standard black and chrome screw mount form, with the small engraving differences on the beauty ring being the most notable variation [3].

Collector Notes Before buying, check the optics for haze and the faint internal fungus that affects many surviving Komura lenses, since these are common on examples that have sat unused [1]. Expect a focus action that may be stiff and benefit from a clean and re-lube, and be aware that rangefinder coupling on an individual sample may need shimming or adjustment to agree with the camera, particularly when adapting to Leica M [1]. The lens shares its general look and naming with other Komura screw mount telephotos, so confirm the focal length and aperture engraving rather than relying on the barrel style alone [3]. Original caps and a correctly sized hood are worth verifying, as an over deep hood can introduce vignetting on this short telephoto [2].

Sources

• [1] Cameraderie. Tales from the Greasy Side: Komura 105mm F3.5 Teardown. https://cameraderie.org/threads/tales-from-the-greasy-side-komura-105mm-f3-5-teardown.48007/
• [2] Rangefinderforum. KOMURA 105mm 3.5 LTM with M10. https://rangefinderforum.com/threads/komura-105mm-3-5-ltm-with-m10.4754789/
• [3] Camerapedia. Sankyō Kōki. https://camerapedia.fandom.com/wiki/Sanky%C5%8D_K%C5%8Dki
• [4] Kamera Manufaktur. Sankyo Kohki and the Komura lenses. https://kameramanufaktur.jimdofree.com/lenses/komura-lenses/