For the record, Olympus was first known as K.K. Takachiho Seisakusho (Takachiho Works Co., Ltd.), a manufacturer of microscopes and thermometers, established and in production from 1920. As an 'approved company' supplying microscopes to the Navy, Olympus also supplies an apparatus to take pictures with a microscope, a ground glass dark-box with a prism and a basic shutter mechanism.
The beginning of Olympus as a camera manufacturer started in 1934 with the first serially produced lens, a four-element Zuiko 75mm f/4.5. The lens was fitted to a body from the Semi Proud, branded and commercialized as the Semi-Olympus I.
Medium Format Photography
Semi-Olympus I (1936)
Hold the camera horizontally, and you will find the advance knob is at the bottom right with film advance is controlled by red windows. The four-element Zuiko 75mm f/4.5 engraved Takatiho Tokyo Zuiko 1:4.5 f=75mm. No.1xxx focuses by turning the front element.
The Semi-Olympus I with the Compur shutter version comes with a T, B, 1–250 speeds, and has a self-timer and a thread to attach a cable release, while the later with Rulex shutter comes with a 1–200, B, T speeds, a thread for a cable release but no self-timer.
Semi-Olympus II (1938)
The form factor of the Semi-Olympus II is that of a horizontal folding camera, constructed with pressed sheet-metal body with a side-opening design. It is fitted with the same Zuiko 75mm f/4.5 lens as on the previous Semi Olympus.
Olympus Six (1940)
There are strap lugs at both ends of the top plate now, which replaces the leather handle of the previous model, and no accessory shoe. With this camera, Olympus established the basic format for subsequent Six-series cameras. Lenses mounted on the Olympus Six are the four elements Zuiko 75mm f/4.5 (same as on the Semi Olympus and Semi Olympus II) and the new Zuiko 75mm f/3.5.
Olympus Chrome Six I (1948)
All Olympus Chrome Six models have front-cell focusing 75mm Zuiko lenses, with either f/3.5 or f/2.8 aperture, and Copal shutter except for some very early cameras. Olympus Chrome Six I, II and III have a flat all-chrome top plate, a tubular finder with parallax indications and translucent blue strips showing the field of view for 4.5 × 6 cm exposures.
Olympus Chrome Six IIIA (1951)
Olympus Chrome Six RIIA (1955)
The body design was also innovative, and the film winder was changed to a lever on the reverse of the body, and an automatic winder stop system was added. This camera, and the V, which had no range-finder, were the last models in the Six series.
Olympus Flex I (1952)
The shutter is a Seikosha-Rapid (B, 1–400), in #0 size. Both lenses are 75mm f/2.8 with bayonet filter attachments. The taking lens is a six-element F.Zuiko F.C. and the viewing lens is a Zuiko F.C. Though modeled on the Rollei Flex, the camera incorporated numerous unique Olympus features.
Olympus Flex A3.5 (1954)
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Note: A slightly edited version of this article has previously been posted on my account on HubPages, which is being depreciated.