Simlar (シムラー) lenses were made by Tōkyō Kōgaku (predecessor of Topcon) from c.1935[1] to 1955. The name Simlar (written shimurā in Japanese) is derived from Shimura (志村), a place name in Tokyo where the company plant was located.[2] The Simlar brand was originally used for a four-element lens design, copy of the Tessar. From the late 1930s or early 1940s, the name was applied to all the lenses made by Tōkyō Kōgaku with advanced specifications, as opposed to the Toko or State brands, used for three-element lenses. In 1955, the names Toko and Simlar were replaced by the single brand name Topcor.

Simlar lenses in leaf shutters, for civilian cameras[]

Simlar 6cm f/3.5[]

The Simlar 6cm f/3.5 was mounted on the Minion III, introduced during World War II but mainly sold in the postwar period.

Simlar 7.5cm f/3.5[]

At least one example of the Simlar 7.5cm f/3.5 was mounted on a Lord by Tōkyō Kōgaku, made c.1937–8, though the camera was normally advertised with a Toko 7.5cm f/3.5 three-element lens.

Simlar 10.5cm f/4.5[]

The Simlar 10.5cm f/4.5 was offered from c.1935 on the First, Special First, First Etui and First Roll, made by Kuribayashi and distributed by Minagawa. The lens was normally paired with a Seikosha shutter (T, B, 1–250). These cameras were certainly the first equipped with a Simlar.

The same lens was also mounted on the Luxury Pearl and New Lily released in 1937 by Konishiroku, in combination with a Leo shutter, name variant of the Seikōsha.

Simlar interchangeable lenses, for rangefinder cameras[]

See the main article on Tōkyō Kōgaku lenses in Leica screw mount.

Other Simlar lenses[]

Regular barrel lenses[]

The Simlar lens was offered in barrel mount for general use in large-format cameras, both before and after World War II.[3] It is said that various focal lengths were offered.[3] Examples of a 21cm f/4.5 are known,[4] and a 18cm f/4.5 is reported.[5] On the 21cm f/4.5, the barrel is black and is surrounded by an aperture ring graduated from 4.5 to 45. The focal length 21cm is repeated next to the aperture scale.

Aerial lenses, for military use[]

The Simlar 7.5cm f/3.5 was mounted on the GSK-99 aerial camera. The Simlar is normally found on those cameras made by Tōkyō Kōgaku, whereas those made by Konishiroku normally have a Hexar.

Simlar 180mm f/4.5 lenses were made for the larger SK-100 aerial camera. The lenses are engraved with the precise focal length, for example 179.5mm or 180.2mm on the actual examples photographed in this page.

A Simlar 300/4.5 has been reported by a dealer, with serial number 2, but nothing else is known about that lens.

Finally, Tele-Simlar 40cm f/5 lenses were used on some aerial cameras, such as the Type 1 vertical mapping camera by Tōkyō Kōgaku, displayed in the Smithsonian National Air and Space Museum.[6]

Wide-aperture lenses[]

Simlar 50mm f/1.5[]

The Simlar f/1.5, designed by Tomita[7] Ryōji (富田良治),[8] was the first wide-aperture lens developed by Tōkyō Kōgaku. The design has seven elements in four groups.[8] A patent for that lens was filed in November 1938 and published in June 1940.[8] In the patent, reproduced below, the lens is mentioned as a "photography lens" (写真鏡玉), and a scheme is drawn for a 100mm f/1.5.[8]

The lens was first manufactured as a 50mm f/1.5 for X-ray photography, made from c.1941.[9] It was mounted in a fixed rigid barrel on a special X-ray camera made by an unknown manufacturer, perhaps Tōkyō Kōgaku itself.[10] It has been said that at least some lenses were supplied to the 2nd Army Aeronautical Engineering Institute of Tachikawa,[11] but this might be a confusion with the 50mm f/0.7 (see below).

After World War II, the lens was produced in Leica screw mount and sold on the Leotax, see Tōkyō Kōgaku lenses in Leica screw mount.

Wartime Simlar 50mm f/0.7[]

The first Simlar[12] 50mm f/0.7 was designed by Maruyama Shūji (丸山修治)[13] — who later worked for Norita.[14] The development of an ultra-high aperture lens was ordered by the military towards the end of 1943, and the lens was completed in Summer 1944.[15] The most detailed account of the story is given in the December 1951 issue of Asahi Camera, reproduced below.[16] The lens was also mentioned in an article dated 23 Oct. 1951 of the daily newspaper Mainichi Shinbun, which mainly addresses the 5cm f/0.7 postwar evolution.[17] (Remarkably, the article in Asahi Camera makes no mention of the postwar lens.)

The lens has eight elements in four groups.[18] The angle of view is 30 degrees, and the coverage is good enough for 24×24mm exposures.[19] The lens was originally developed for night reconnaissance photography.[20] However, before it could be extensively tested for its intended use, the few examples made were claimed by the Aeronautical Engineering Institute of Tachikawa for X-ray medical photography.[21] The lenses would have been part of an experiment to learn about the effects of high acceleration on the human heart during the pull-out manoeuvre after dive bombing.[22] It seems that the rest of the equipment needed for the experiment was never built — perhaps not even the camera — and nothing came out of the project.[23]

The December 1951 article in Asahi Camera says that ten units were made until the end of the war, but their fate was unknown except for one example, still held by Maruyama Shūji at Tōkyō Kōgaku at the time.[24] The article in Mainichi Shinbun says that Life's reporter David Duncan wanted to borrow a Simlar f/0.7 at some point; the phrasing seems to imply that the story applies to the wartime version (maybe Maruyama's own example), and that Duncan did not actually obtain the lens.[25] Various later sources say that one or several examples were transferred to the U.S. forces after World War II;[26] all these seem to repeat a piece of information that was perhaps in Tōkyō Kōgaku's fifty-year history book, printed in 1982.

At least one surviving example of the wartime 50mm f/0.7 has been recently photographed;[27] it is very likely that this example was the one mentioned in Asahi Camera December 1951 and pictured in the hands of Maruyama Shūji. It has a large black barrel, 128mm long and 90mm in diameter, and weighs 1kg.[28] There is a fine screw thread at the base of the barrel, 66mm in diameter and 0.5mm in thread.[28] The flange-to-film register is 33.3mm, but the lens rear element is only 7mm away from the film plane.[28] The aperture ring is graduated from f/0.7 to f/8, and the diaphragm has 18 blades.[28] It seems that the lens has no focusing ring, but this is not entirely clear.[29] The surviving example has serial number 5,[30] and is engraved Simlar 1:0.7 f=50mm Tokyo Kogaku Nr.5 around the rim.[31]

Postwar Simlar 5cm f/0.7[]

The Simlar 5cm f/0.7 is a postwar evolution of the previous lens. The 1951 article in Mainichi Shinbun, already cited above, says that the lens design was improved by Maruyama Shūji after the end of the war.[32] These modifications were rather minor: the formula is the same as the wartime lens (eight elements in four groups), and the optical scheme looks very similar.[33] Lens coating, absent from the wartime lens, was applied to the postwar version.[34]

The Mainichi article goes on saying that three examples were made, two of which were used by the newspaper for an expedition to the South Pole.[32] No detail is known of the camera used in that expedition.

The Simlar 5cm f/0.7 lens was still listed in a catalogue of Tōkyō Kōgaku products showing the Topcon 35A, 35B and 35-S, dating c.1956.[35] No price is given in this document, but this is perhaps an indication that the lens was still available on special order, and that more than three were made after all.

At least one surviving example of the lens is known, with serial number 100002, either the second or third produced. Judging from the available pictures, it seems that this lens has hardly any traces of use;[36] it is likely that this example was not one of those sent to the polar expedition.

The lens weighs 2,500g, much heavier than the wartime version.[37] The barrel is 105mm in diameter and 123.7mm in length.[37] The lens is all chrome, except for a black beauty ring at the middle of the barrel, engraved Simlar 1:0.7 f=5cm Tokyo Optical No.100002.[38] The aperture ring, graduated from f/0.7 to f/8, is less massive than on the wartime lens, and the diaphragm only has thirteen blades.[37] The base of the barrel has a square plate with four screw holes, to attach the lens on a camera. The flange-to-film distance is 30.3mm, and the distance from the rear element to the film plane is 7mm, same as on the wartime design.[37] The lens reportedly has focusing ability from 3m to infinity, but this is unconfirmed.[39]

Besides the f/0.7 lens, it is said that a 50mm f/0.75 design was also computed,[40] but it seems that it was never made.

Simlar 13cm f/1[]

The Simlar 13cm f/1 was developed by Tomita Ryōji as an ultra-wide aperture lens for night photography.[41] The lens was attached to a special 6.5×9cm camera, essentially consisting of a modified Miroflex shutter unit with the huge lens at the front and a small tubular finder at the top (see Japanese night camera).

The only known surviving example is attached on such a camera, and has serial number 1. It has a huge black barrel with a massive aperture ring, graduated from f/1 to f/8.[42] The outer rim is engraved Simlar 1:1 f=13cm Tokyo Kogaku K.K. Nr.1.[42] It is not known if any other example was ever manufactured, and if the lens was actually used in operation.

Simlar-F 180mm f/1.5 and 200mm f/2[]

The Simlar-F 180mm f/1.5 was a high aperture lens for night aerial photography assisted with magnesium flash bombs.[43] The synchronization of the camera's shutter to the flash illumination system was developed in cooperation with Tōshiba.[43] It is said that the project was developed from 1940.[43]

A single surviving example of the lens is known, pictured in this page by Akiyama Michio. This huge lens comes in a large wooden box, with an identification plate inscribed 東京光学機械株式会社製造 ("Made by Tōkyō Kōgaku Kikai"), 第5號 ("Serial number 5") and 昭和17年3月製 ("Made in March 1942"). The lens barrel is all black, with a fine screw thread approximately in the middle section. The aperture ring is graduated from f/1.5 to f/8. The side of the barrel is engraved Simlar–F 1:1.5 f=180mm Tokyo Kogaku No.5 with Tōkyō Kōgaku's triangular logo. It seems likely that the "F" in the name stands for Flash.

It is said that Tōkyō Kōgaku also developed a 200mm f/2, apparently for the same project.[43] This lens was developed by the company on its own, without any official order;[43] it is not known if it was actually used.


  1. Various sources say that the Simlar was introduced in 1937, but the lens is already mentioned in advertisements dated 1935 for the First, First Etui and First Roll.
  2. Shirasawa, p.15, and this page of the Topcon Club.
  3. 3.0 3.1 Shirasawa, p.63.
  4. Examples pictured in Shirasawa, p.63, and in this page of the Topcon Club.
  5. The 18cm f/4.5 is reported in this page of the Topcon Club, where it is said to be mentioned in Kurashikku Kamera Senka no.15.
  6. Example pictured in this page of the NASM, and example pictured in this page of the Topcon Club.
  7. The name is spelt "Tonita" by mistake in Baird, p.72, and Antonetto and Russo, p.195.
  8. 8.0 8.1 8.2 8.3 Patent publication (特許広告) no.S15-3014, available in the IPDL trademark database
  9. Shirasawa, p.50.
  10. Camera pictured in Shirasawa, p.51.
  11. Shirasawa, p.51, mentions the "Aeronautical Institute of Tachikawa" (立川の航空研究所). The exact name is given in this page of the Japanese Wikipedia.
  12. The wartime f/0.7 lens is called "Toko" in various websites, but this name is wrong. It seems that the mistake originates in this page of the Topcon Club, and has spread out elsewhere.
  13. Column in Asahi Camera December 1951, p.84, and extract of an article in the Mainichi Shinbun Oct. 23, 1951 quoted in Shirasawa, p.52: 丸山修治氏より完成したシムラー0.7. On p.51, Shirasawa says that the lens was designed by Tomita Ryōji, but this is apparently a mistake.
  14. This page of the Topcon Club.
  15. Column in Asahi Camera December 1951, p.84. — The lens is dated c.1941 (apparently by mistake) in Shirasawa, p.51, 1943 in Antonetto and Russo, p.26, and 1944 in Lewis, p.184, and Baird, p.72.
  16. Column in Asahi Camera December 1951, p.84.
  17. Article in Mainichi Shinbun, Oct. 23, 1951 quoted in Shirasawa, p.52.
  18. Scheme in Shirasawa, p.55. The column in Asahi Camera December 1951, p.84, also mentions eight elements.
  19. Column in Asahi Camera December 1951, p.84. — Shirasawa, p.51, says that the image circle has 26mm diameter, certainly after the scheme reproduced on p.55. However it seems that the 26mm size does not correspond to the diameter of the image circle (or diagonal of the actual image) but to the maximal width considered for the image frame.
  20. Column in Asahi Camera December 1951, p.84: 夜中でも観測ができるような観測器ノクト・ヴィジョンの設計を始めた.
  21. Column in Asahi Camera December 1951, p.84: ところが苦心のレンズ数個を一応軍に納入し、その成果をまだ見ないうちに、こんどは立川の航空技術研究所の医学関係からそのレンズをオレの方へ回せという要求がきた. The article in Mainichi Shinbun, Oct. 23, 1951 quoted in Shirasawa, p.52, says that the lens could take pictures at 1/5s in the moonlight, and could be used for X-ray photography too: 満月の夜には5分の1秒のシャッターが切れる。レントゲン蛍光板の連続撮影も出来た。
  22. Column in Asahi Camera December 1951, p.84: それは航空機が急降下爆撃をして機体を引起す際、加速度により心臓がどんな変化を起すかを、レントゲンの間接撮影で研究しようという目的から、レントゲン栄光板に写る淡い像を明るいレンズで撮影しようというためであった.
  23. Column in Asahi Camera December 1951, p.84: いずれの場合も、レンズ以外の部分の構造外観などは、最後までついに明らかにされなかったという.
  24. Column in Asahi Camera December 1951, p.84.
  25. Extract of an article in the Mainichi Shinbun Oct. 23, 1951 quoted in Shirasawa, p.52: ライフ特派員ダヴィッド・D・ダンカン氏は貸与を申し入れた。 (The sentence appears after a discussion of the wartime lens, and before the mention of a modified postwar design.)
  26. Baird, p.72, says that a prototype "was purchased by and transferred to the United States". — Lewis, p.184, says that the lens was "sold to the U.S. occupation forces" — Antonetto and Russo say on p.26 that the lens "was acquired by the U.S. Air Force after the war", and on p.196 that the Simlar f/0.7 was produced for the U.S. Air Force after 1945.
  27. Example pictured in Shirasawa, pp.54–5.
  28. 28.0 28.1 28.2 28.3 Specifications in Shirasawa, pp.53–5.
  29. Shirasawa, p.53, mentions focusing ability "from 0.7mm to ∞", but the pictures do not show a distance scale or focus ring (and the minimum distance is obviously wrong).
  30. Antonetto and Russo, p.195, say that "only a prototype was produced", but this is certainly wrong.
  31. Pictures in Shirasawa, pp.54–5, and specifications on p.53.
  32. 32.0 32.1 Extract of an article in the Mainichi Shinbun Oct. 23, 1951 quoted in Shirasawa, p.52: 戦後、改めて丸山氏が設計試作を行い3台完成し、後に南極探検隊用として毎日新聞社に2台納入されたが、量産には移されなかった。
  33. Schemes in Shirasawa, p.55.
  34. Shirasawa, pp.53–4.
  35. Tōkyō Kōgaku catalogue certainly dated 1956, reproduced in this page of the Topcon Club website.
  36. Pictures in Shirasawa, pp.54–5.
  37. 37.0 37.1 37.2 37.3 Specifications in Shirasawa, pp.54–5.
  38. Pictures in Shirasawa, pp.54–5, and specifications on p.54.
  39. Shirasawa, p.54, mentions focusing ability from 3m to ∞, but the focus ring is not clearly visible in the pictures.
  40. Shirasawa, p.53.
  41. Shirasawa, pp.54–5, quoting the book Nihon no kōgaku kōgyō-shi.
  42. 42.0 42.1 Pictures and specifications in Shirasawa, pp.55–6, and in Kurashikku Kamera Senka no.49, pp.82–3.
  43. 43.0 43.1 43.2 43.3 43.4 Shirasawa, p.55.



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