Semi Oscon

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Japanese Semi (4.5×6)
Postwar models (edit)
Apollo | Semi Blond | Semi Crystar | Daido Semi | Doris | Semi Frank | Semi Gelto | Semi Golder | Karoron | Karoron RF | Kely | Kiko Semi | Korin | Kuri | BB Kuri | Lark | Semi Leotax | Semi Leotax DL / R | Lo Ruby | Semi Lord | Luck | Semi Lyra | Semi Masmy | Middl 120 | Semi Mihama | Mikado | Million Proud | Semi Minolta III | Semi Minolta P | Semi Oscon | Semi Pearl | Pearl I–III | Pearl IV | Petri | Petri RF | Petri Super | Pioneer | Semi Proud | Semi Rocket | Rocky Semi | Rosen | Ruby | Shinkoh Rabbit | Semi Sport | Tsubasa Semi | Union Semi | Union Model U | Walcon Semi | Waltax | Semi Wester | Zenobia
rigid or collapsible
Semi Dak | Semi Hobix | Super Semi Plum | Rocket Camera | Tomy
Prewar and wartime models ->
Japanese SLR, TLR, pseudo TLR and stereo models ->
Japanese 3×4 and 4×4, 4×5 and 4×6.5, 4.5×6 and older 6×9 ->

The Semi Oscon (セミ・オスコン) is a Japanese 4.5×6 folding camera distributed by Ōsawa Shōkai in 1953 and 1954.[1] It is said that it was made by Yamagata Kikai, a company affiliated with Tōkyō Kōgaku.[2]


The Semi Oscon is a vertical folder with a die-cast body. The top housing is placed on the right, as seen by the photographer holding the camera vertically, the reverse of the usual arrangement. The body release is tripped by the right hand's finger. The Semi Oscon has automatic stop advance. The advance knob is at the left end, near the folding bed release button, and it seems surrounded by an exposure counter.

The viewfinder protrudes from the top housing; it is slightly offset to the left. Above the viewfinder is a folding sports-finder, with a bar in the middle of the front frame. There is an accessory shoe to the right of the finder and a dial on the right of the top plate, which seems to be a film reminder. The back is hinged to the right.

The folding struts are engraved with a YK logo (certainly for Yamagata Kikai), and an Oscon nameplate is screwed to the front of the body. The name Oscon is embossed in the leather case too.

The Semi Oscon has a Toko 75mm f/3.5 coated lens made by Tōkyō Kōgaku. The shutter is an NKS-TB, gives B, 1–200 speeds and has a self-timer and a PC synch post.

The only surviving example observed so far is pictured in Sugiyama.[3]


The camera was advertised by Ōsawa Shōkai in August, September and December 1953,[4] together with the Primoflex or Topcon 35 cameras made by Tōkyō Kōgaku. The advertisements ambiguously suggest that the Semi Oscon was made by this company too, and they do not mention Yamagata. (For example, in this advertisement dated 1954, reproduced in the Shashin-Bako website, we read the following: "Applaused cameras by Tōkyō Kōgaku, representing the Japanese optical world", translation of "日本の光学界を代表する東京光学の絶讃カメラ"). This is obviously intentional: Tōkyō Kōgaku was a reputed company whereas Yamagata Kikai was virtually unknown.


  1. Dates: articles and advertisements listed in Kokusan kamera no rekishi, p.348.
  2. Attribution to Yamagata: Kokusan kamera no rekishi, p.348, Lewis, p.79, Sugiyama, item 1381. Affiliated with Tōkyō Kōgaku: See the chronology of the Topcon official website and the chronology of the Topcon Yamagata official website. Lewis, p.79, Sugiyama, item 1381, and Tanaka, p.79 of Kurashikku Kamera Senka no.8 say that Yamagata Kikai was related to Nippon Kōgaku, certainly by mistake.
  3. Sugiyama, item 1381.
  4. Advertisements published in Asahi Camera, reproduced in Kokusan kamera no rekishi, pp.124 and 175.