History of the single-lens reflex camera

The history of the single-lens reflex camera (SLR) begins with the use of a reflex mirror in a camera obscura described in 1676, but it took a long time for the design to succeed for photographic cameras. The first patent was granted in 1861, and the first cameras were produced in 1884, but while elegantly simple in concept, they were very complex in practice. One by one these complexities were overcome as optical and mechanical technology advanced, and in the 1960s the SLR camera became the preferred design for many high-end camera formats. The advent of digital point-and-shoot cameras in the 1990s through the 2010s with LCD viewfinder displays reduced the appeal of the SLR for the low end of the market, and in the 2010s and 2020s smartphones have taken this place. The SLR remained the camera design of choice for mid-range photographers, ambitious amateur and professional photographers well into the 2010s, but by the 2020s had become greatly challenged if not largely superseded by the mirrorless interchangeable-lens camera, with notable brands such as Nikon and Canon having stopped releasing new flagship DSLR cameras for several years in order to focus on mirrorless designs.

Early large and medium format SLRs The photographic single-lens reflex camera (SLR) was invented in 1861 by Thomas Sutton, a photography author and camera inventor who ran a photography related company together with Louis Désiré Blanquart-Evrard on Jersey. Only a few of his SLRs were made. The first production SLR with a brand name was Calvin Rae Smith's Monocular Duplex (USA, 1884). Other early SLR cameras were constructed, for example, by Louis van Neck (Belgium, 1889), Thomas Rudolphus Dallmeyer (England, 1894) and Max Steckelmann (Germany, 1896), and Graflex of the United States and Konishi in Japan produced SLR cameras as early as 1898 and 1907 respectively. These first SLRs were large format cameras. While SLR cameras were not very popular at the time, they proved useful for some work. These cameras were used at waist level; the ground glass screen was viewed directly, using a large hood to keep out extraneous light. In most cases, the mirror had to be raised manually as a separate operation before the shutter could be operated. As with camera technology in general, SLR cameras became available in smaller and smaller sizes. Medium format SLRs soon became common, at first larger box cameras and later "pocketable" models such as the Ihagee Vest-Pocket Exakta of 1933.

Development of the 35 mm SLR

The first 35mm prototype SLR was the "Filmanka" developed in 1931 by A. Min in the Soviet Union. In 1933 A.O. Gelgar developed the "GelVeta" also in the USSR, later renamed Спорт ("Sport"). "Sport" was a very smart design with a 24mm × 36mm frame size, but, according to some sources, it did not enter the market until 1937, although there is now some evidence emerging that "Sport" may have been in limited production before 1936. Because of the probable production in small numbers it has been claimed not to be the first mass-produced 35mm SLR.

Early innovations Early 35 mm SLR cameras had functionality that was similar to larger models, with a waist-level ground-glass viewfinder and a mirror that remained in the taking position and blacked out the viewfinder after an exposure, and then returned when the film was wound on. Innovations that transformed the SLR were the pentaprism eye-level viewfinder and the instant-return mirror—the mirror flipped briefly up during exposure, immediately returning to the viewfinding position. The half-silvered fixed pellicle mirror, without even the brief blackout of the instant-return mirror, was also innovative but did not become standard. Through-the-lens light metering was another important advance. As electronics advanced, new functionality, discussed below, became available.

Exakta

The first 35mm format SLR in large scale production was the Ihagee Kine Exakta, produced in 1936 in Germany, which was fundamentally a scaled-down Vest-Pocket Exakta. This camera used a waist-level finder. Various other models were produced, such as the Kine-Exakta, the Exakta II, the Exakta Varex (featuring an interchangeable pentaprism eye-level viewfinder and identified in the United States as the 'Exakta V'), the Exakta Varex VX (identified in the United States as the 'Exakta VX'), the Exakta VX IIa, the Exakta VX IIb, the Exakta VX500 and the Exakta VX1000. Ihagee also manufactured less expensive cameras under the 'Exa' camera label, such as the Exa, the Exa Ia, the Exa II, the Exa IIa, the Exa IIb (which was generally not considered part of the "official" Exa line), and the Exa 500. The Exacta sold well and triggered other camera manufacturers to develop 35mm SLRs. Sales were particularly strong in the medical and scientific fields. A large range of lenses and accessories were made by a variety of manufacturers, turning the camera into one of the first system cameras, although motor drives and bulk loading backs were never produced by Ihagee.

Rectaflex Rectaflex was the name of an Italian camera maker from 1947 to 1958. It was also the name of their sole model. The Rectaflex was a 35 mm SLR camera with a focal plane shutter, interchangeable lenses, and a pentaprism eye-level finder. Rectaflex (followed by Contax S) was the first SLR camera introducing the modern pentaprism eye-level finder. The first prototype (Rectaflex 947) was presented in 1947, with a final presentation in April 1948 and start of series production (A 1000) in September the same year, thus hitting the market one year before the Contax S, presented in 1949. Both were preceded by Alpa-Reflex, first presented to a wider public in April 1944 at the Swiss Trade Fair in Basel (Schweizer Mustermesse). Alpa's production was slow up to 1945, and it lacked a pentaprism, so the image was reversed left-to-right.

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