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Yamasaki Kōgaku Kenkyūsho (山崎光学研究所, meaning Yamasaki Optical Laboratory) is a Japanese lens maker.

See also the company Yamasaki Seiki Seisakusho which made the Bonny cameras in the first half of the 1940s and is probably unrelated, and the Congo Camera taking no-need-darkroom film stock.


K. Yamasaki (山崎光七),[1] founder of the company, was a former employee of Asanuma Shōkai.[2] He opened a camera shop called Shūzandō Yamasaki Shōten (秀山堂山崎商店) in 1924 and worked in the shop's basement after business hours to develop a camera lens.[3] The result of this hard work was the Congo 210/4.5 lens released in 1931.[4] Yamasaki has used the name "Congo" (コンゴー, Kongō) for its lenses since that date. The Japanese word kongō (金剛) conveys the idea of indestructibility and is found as a compound in the word "diamond" (金剛石, kongōseki); however it is said that the lenses were actually named after the Japanese battleship Kongō (金剛, usually spelled "Kongo" in English contexts), built in Britain as a battle cruiser in 1911 and sunk in 1944,[5] itself named after the 1112m-high Mt Kongō (金剛山, Kongō-san) on the Ōsaka/Nara border.[6]

The company was incorporated as K.K. Yamasaki Kōgaku Kenkyūsho (㈱山崎光学研究所, Yamasaki Optical Co., Ltd.) in 1955.[7] It is based in Hino-shi, suburban Tokyo (山崎光学研究所) since 1972.[8] It has concentrated on lenses for large-format cameras.

Yamasaki seems to buck stereotypes about Japanese companies. It caters for a niche market, advertises little, and sells directly via mail and its website; the FAQ in its website answers just three questions, of which the first is of why the prices are so low.[9]

Japanese folders fitted with Congo lenses

All date to the period 1951 to 1954:

Congo lenses

A prewar advertisement for the Congo lenses lists the following:[10]

  • 150/4.5 (¥42)
  • 180/4.5 (¥50)[11]
  • 210/4.5 (¥58)
  • 300/4.5 (¥135)
  • 210/6.3 (¥28)
  • 300/6.3 (¥75)

The catalogue by Asanuma Shōkai dated July 1938 mentions Congo f/4.5 four-element lenses[12] and Congo f/6.3 triplet lenses lenses, along with a Wide-Angle Congo 12cm f/7 covering kabine format, advertised as the first Japanese wide-angle lens.[13]

The catalogue by Asanuma Shōkai dated October 1941 gives the following list of Congo lenses:[14]

  • 150/4.5, tefuda format, four elements (¥71.90);
  • 180/4.5, kabine format, four elements (¥84);
  • 210/4.5, kabine format, four elements (¥101.10);
  • 210/6.3, kabine format, three elements (¥41.65).

An advertisement by Yamasaki dated 1960 still mentions Asanuma Shōkai as authorized dealer and shows the following product lines:[15]

  • large format camera lenses, from 135mm to 300mm, 12 models
  • small format camera lenses, from 35mm to 150mm, 13 models
  • enlarging lenses, from 50mm to 135mm, 7 models
  • projection lenses for 8mm movies: 18/1.2, 19/1.6, 25/1.4

The current lens range (as of 2015) consists of:[16]

  • Comercial Congo - Tessar, standard lens from 90 to 360 mm (4 elements in 3 groups)
    • Commercial Congo 90/3.5 (6×9cm)
    • Commercial Congo 105/4.5 (6×9cm)
    • Commercial Congo 135/4.7 (3×4")
    • Commercial Congo 135/4.7 (4×5")
    • Commercial Congo 150/4.5 (4×5")
    • Commercial Congo 150/6.3 (4×5")
    • Commercial Congo 180/6.8 (5×7")
    • Commercial Congo 210/6.3 (5×7")
    • Commercial Congo 240/6.3 (5×7")
    • Commercial Congo 250/6.3 (6×8")
    • Commercial Congo 300/6.3 (8×10")
    • Commercial Congo 360/6.8 (10×12")
  • Tele-Congo - Simple tele lens (4 elements in 2 groups)for 4x5"
    • Tele-Congo 300/8 (4×5")
    • Tele-Congo 400/8 (4×5")
    • Tele-Congo 500/9.5 (4×5")
  • Wide Angle Congo - Symmetrical wide Angle (4 elements in 4 groups)
    • Wide Angle Congo 90/6.3 (4×5")
    • Wide Angle Congo 120/6.3 (5×7")
  • Soft focus Congo - Triplet lens (3 elements in 3 groups)
    • Soft Focus Congo 150/4 (4×5")
    • Soft Focus Congo 200/4 (Cabinet size)
  • Alto-W - Plasmat lens (6 elements in 4 groups)
    • Alto-W 180/5.6 (5×7") (not available in 2014)
    • Alto-W 210/5.6 (6×8")


  1. The first name perhaps reads Kōichi. See Baird, p.59.
  2. Yamasaki history page; Inoue, p.130; Baird, p.59.
  3. Name of the shop: Inoue, p.130. 1924 date: Yamasaki history page and Baird, p.59. Working after office hours in the basement: Inoue, p.130; Baird, p.59.
  4. Yamasaki history page; Inoue, p.130. Baird, p.59, says 1932.
  5. Niimi, p.102; Inoue, p.130.
  6. See this page about the battleship.
  7. Yamasaki history page.
  8. Yamasaki history page.
  9. Yamasaki Optical FAQ.
  10. Advertisement by Asanuma Shōkai for the Congo lenses, reproduced in Inoue, p.130.
  11. Seen in Jan. 2011 in a Japanese online auction with sn 13237 (part of an Asanuma kabine-format camera).
  12. Actual example of a Asanuma King Kansha-Gō (感謝號, "Gratitude" Model) kabine-format (12 × 16.5 cm) field camera fitted with K. Yamasaki Tokyo Congo 21cm f/4.5 lens (sn 27617).
  13. Catalogue by Asanuma Shōkai dated July 1938, p.10.
  14. Catalogue by Asanuma Shōkai, dated October 1941, p.16. The number of elements is mentioned on p.7.
  15. Advertisement published in Asahi Camera Annual '60.
  16. Congo lens specifications in the Yamasaki official website.

Sources / Further reading

  • Asahi Camera Annual '60 (アサヒカメラ年鑑'60). Tokyo: Asahi Shinbun-sha, February 25, 1960. No ISBN number. Advertisement by Yamasaki Kōgaku Kenkyūjo.
  • Asanuma Shōkai. Cameras and other apparatus and materials. Catalogue dated July 1938. P.10. Document partly reproduced in this Flickr album by Rebollo_fr.
  • Asanuma Shōkai. Shashinki to zairyō (Cameras and supplies). Catalogue dated October 1941. Pp.7 and 16. Document partly reproduced in this Flickr album by Rebollo_fr.
  • Baird, John R. The Japanese Camera. Yakima, WA: Historical Camera Publications, 1990. ISBN 1-879561-02-6. Pp.58–61.
  • Inoue, Mitsuo (井上光朗). "Shashin renzu no yoake. Renzu-ya Funsenki" (写真レンズの夜明け・レンズ屋奮戦記, Dawn of the photographic lens — Fierce war tales between lens shops). Kamera Rebyū: Kurashikku Kamera Senka (カメラレビュー クラシックカメラ専科) / Camera Review: All about Historical Cameras no.14, October 1989. No ISBN number. Rikō kamera no subete (リコーカメラのすべて, special issue on Ricoh). Pp.128–32.
  • Niimi Kahee (新見嘉兵衛). Kamera-mei no gogen sanpo (カメラ名の語源散歩, Strolls in the etymology of camera names). 2nd ed. Tokyo: Shashin Kōgyō Shuppansha, 2002. ISBN 4-87956-060-X.


In English:

In Japanese: