In May 1961, LA SPIROTECHNIQUE, a French offshore machinery development company, developed a new type of 135-format watertight camera, the Calypso (named for a nymph in Greek mythology), and contacted us through what was then Teikoku Sanso KK (presently Teisan Co.) about commercial production and marketing.
In 1956 we developed an underwater housing to hold the Nikon S2 for underwater photography, and introduced the underwater camera in May under the brand name of Nikon Marine. Then, we made improvements by combining the bodies of SP and S3 in addition to the body of S2 (No.66141001 and later) with the W-Nikkor 3.5 cm f/2.5 and W-Nikkor 2.8 cm f/3.5 lenses, to enable us to use the W-Nikkor 3.5 cm f/1.8 lens. However, the housing-based Nikon Marine was heavy and expensive, and quite different from the Calypso in the technological and functional aspects as well as in marketability.
Realizing that this product involved original ideas, had sufficiently high performance, and its export potential was promising with higher marketability, we formed a technical tie-up with LA SPIROTECHNIQUE in January 1962, and acquired the exclusive production rights and also the exclusive sales rights except in France and the EEC (the European Economic Community of that time).
The underwater camera offered a variety of features including those listed below, with the aid of complete air-tightness provided by the O-ring and the perfect waterproofing in the die-cast sections.

We at Nikon considered this camera as an All-Weather Camera for its highly water-tight, pressure-resistant, and corrosion-resistant properties and other durable mechanisms not achieved by any other cameras, and decided to sell it under the brand name of NIKONOS.
W NIKKOR 35 mm f/2.5 for use both underwater and in air, and a little later, underwater-specific wide-angle lens, U·W NIKKOR 28 mm f/3.5 were made available. In addition, flashguns essential to underwater color photography were also made available.
The front waterproof glass of the 35 mm f/2.5 lens was flat, while the underwater-specific 28 mm f/3.5 lens had a biconvex lens and this waterproof front lens and water combination formed a single lens to help correct any distortion and/or chromatic aberration in the water.
In March 1963, prior to the formal announcement of the introduction, we entered NIKONOS in the 8th Photokina as a new product, and the idea of hanging the NIKONOS in a aquarium in which goldfish were swimming attracted the attention of visitors.

The well-received NIKONOS then evolved into the successor NIKONOS II, which went on sale in 1968 at 23,000 yen. Since then, the original NIKONOS has been known as NIKONOS (version I).

NIKONOS II had a few major improvements as follows: the film wind-up mechanism was changed to a retractable crank from a knob to accelerate the film rewinding; the film pressure plate was improved to a hinged design to facilitate the exchanging of films thanks to a pop-up pressure plate; and the logotype II was inscribed next to the viewfinder window to represent the version II.

Later in 1975, NIKONOS III went on sale at 45,000 yen, featuring the further improved durability and operability of NIKONOS II.
The version III went through some major improvements to its predecessors as follows: a sprocket was adopted for film wind-up, when the wind-up amount in predecessors I and II had to be adjusted by gradually decreasing the angle of rotation of the spool with every frame. This achieved equal frame-to-frame spacings on a roll of film. The frame counter was relocated to the top of camera from the bottom of the body outer casing for more convenient reading. The viewfinder was modified to the illuminating window-type bright frame to provide a brighter field of view and a crisper, clearer frame. And an additional frame for 80 mm lenses was incorporated. Moreover, special considerations were made as follows: the film holding spool was improved to contain two grooves for easier film loading; the flash sync connector was improved; and the hinged pressure plate adopted first in version II was modified to open in the downward direction.

The body became larger in size due to the adoption of sprockets and the illuminating window-type viewfinder. However, the film advance lever was modified to a larger size, and the film rewind crank and shutter release button were redesigned to fit the camera and ensure easier operation even with gloved fingers. The versions I and II were a unique spindle-shaped design in appearance which was said to be resistant to external pressures. The version III inherited the spindle-shaped appearance, though it was getting closer to a box-shaped camera. The logo mark of NIKONOS III was moved under the lens mount of the body outer casing.

NIKONOS I, II and III are modified or improved versions of Calypso, whereas NIKONOS IV-A is regarded as a Nikon's completely original model developed and designed based on Nikon's proprietary concepts. This model was placed on the market in July 1980 at 54,500 yen. It offered a variety of capabilities and its key features are discussed below.

At that time, aperture-priority and other automatic exposure (AE) control systems came into common use among the single-lens reflex (SLR) cameras for use on land, and the IV-A also adopted the AE control mechanism. This model was equipped with the automatic exposure control with through-the-lens (TTL), center-weighted, exposure metering of aperture-priority in order to ensure correct exposure by taking into account the brightness of the edges of the image field while focusing on the center of the image plane. In order to realize the exposure metering system, a reflector was incorporated in front of the shutter blade, working in synchronization with the shutter blade. The reflector reflects the light after it passes through the lens and directs it towards the light-receiving element SPD for exposure metering, and correct exposure is determined based on the amount of light sensed at the SPD. In water, it is difficult to determine optimum exposure, but the aperture-priority AE was well received by many photographers since it could offer an accurate exposure value simply by selecting an aperture.

The model IV-A became a breakthrough camera for its capability to provide automatic exposure control underwater with the aperture-priority AE. In practice, however, the shooting mode was limited to aperture-priority; then, the addition of the manual mode was requested to permit optional selection of shutter speeds. In response to the request, the NIKONOS V incorporated the manual mode in addition to the aperture-priority AE. In addition, the flash control of Speedlights used with IV-A was based on an external sensor; the V made possible the automatic TTL flash control by using the specifically designed Speedlight models including SB-102 and 103. The model V came out in April 1984 at 73,000 yen with a significant evolution in automatic control of exposure and Speedlight. This model also adopted a mechanical shutter to offer a backup shutter speed of 1/90 sec. in the event of a dead battery, and a Bulb setting, as in the case of IV-A. This model was available with a light orange and green body finish colors, which was a somewhat different look from the predecessor versions of NIKONOS series.
The V, brought nearer to perfection, was used not only in underwater photography but also for land photography in bad weather conditions, and remained a long-selling product for as long as 17 years; even though its sale was discontinued in October 2001, it is still missed by many regular users.

Following the first introduction of NIKONOS in 1963, several improvements were made which enabled us to offer our all-weather camera NIKONOS V (Five) (April 1984); during those years, the automatic exposure control and Speedlight made remarkable progress. In practice, however, underwater photography often entails close-up shots due to the lower clarity and bluish color of the water. The use of the NIKONOS series, which involved measuring the distance visually for focusing and framing through the direct optical viewfinder, required a certain level of sophisticate skills.

In addition, an increasing number of users requested for an authentic AF camera specifically designed for underwater photography, without a housing. Consequently, we began plans for the development of a single-lens reflex (SLR) camera to allow easy and accurate focusing and framing, and started the basic investigation in 1986. Later, we became confident that we could provide satisfactory performance underwater with advanced AF technology, and stepped forward with the commercialization of the special underwater AF SLR camera in December 1988.
The newly developed NIKONOS RS AF, which allowed AF photography in water to a depth of 100 m, was added to the lineup of our AF SLR camera series, and was exhibited as a preview at the DEMA Show (January 1992) at Houston, U.S. for diving equipment and materials, PMA Show (February) at Las Vegas, and at the Diving Festival (March) and Japan Camera Show (March) held in Japan, and then released for marketing in June (body alone at the suggested retail price of 390,000 yen, consumption tax excluded).
However, the RS, which aimed to be the ideal underwater camera, required too many processes in manufacturing, and regretfully sale was discontinued in August 1996.