Ōki Kōgaku Seiki Seisaku-sho (大木光学精機製作所, i.e. "Ōki precision machinery factory") was a Japanese company based in Tokyo, Arakawa.[1] It was the producer of two cameras during the Second World War, the Oko Six and Oko Semi. It probably made the four-element Oko or Okor lenses mounted on these cameras. It also made Hildar and Oscar lenses for the Semi Rosen U and Primo distributed by Ōsawa Shōkai.

List of cameras[]

List of lenses[]

The Hildar and Oscar lenses have three elements and are probably identical.[3] The Oko or Okor lens has four elements.[4]

Oscar Anastigmat f/5.6 lenses were also advertised on CH enlargers sold by Misuzu Shōkai.[5]


  1. Its address in 1943 was Tōkyō-to Arakawa-ku Ogu-chō 3–2069 (東京都荒川区尾久町3–2069). Source: "Kokusan shashinki no genjōchōsa" ("Inquiry into Japanese cameras"), listing the Japanese camera production as of April 1943.
  2. Semi Lucky example pictured in McKeown, p. 572.
  3. "Kokusan shashinki no genjōchōsa" ("Inquiry into Japanese cameras"), lens items Lb27, Lb28, Lc6 and Lc7. In the document, the maker's name is missing for the Oscar 75/3.5, but it was surely made by Ōki too.
  4. Advertisements reproduced in Kokusan kamera no rekishi, p.61.
  5. Advertisement in Asahi Camera December 1936, p.A107.