Friedrich Deckel

By 1910, Zeiss had acquired a 16.8% stake in F. Deckel. During World War II, photographic equipment production was paused and F. Deckel made fuel pumps for BMW airplane engines. In 1958, Carl Zeiss AG purchased F. Deckel outright and in 1976 closed down the Compur factor in Munich, consolidating production with Prontor at Calmbach. A portion of the company, responsible for gas monitors, survives as Compur Monitors GmbH. Their FP3 milling machine remained in production until the late years of the 20th Century. Deckel's popular, if expensive, line of industrial tool and cutter grinders remain available for sale under the brand ISOG, a division of Precision Surfacing Solutions. ==Leaf shutter development==

Bruns designed Steinheil's first leaf shutter in 1899, followed by an updated version using a leather brake to control shutter speeds. While at Bruns & Deckel, Bruns developed the Compound leaf shutter in 1905, which had a pneumatic escapement for slow speeds. naming the new shutter Compur as a portmanteau of Compound (from the earlier shutter design) and Uhrwerk (referring to the clockwork mechanism). As introduced, the Compur leaf shutter used a dial to set shutter speeds; the early dial-set versions were succeeded by the rim-set version in 1927, A self-timer mechanism was added in 1928, which was labelled Compur S. The Compur leaf shutter initially provided speeds of up to  sec; the later models (denoted by Compur-Rapid) extended the fastest shutter speed to (#00) and (#0) in 1935. Early versions use three leaf blades, while Compur-Rapid versions used five. Flash synchronization was added via a coaxial PC terminal on the rim of the shutter in 1951, which bore the Synchro-Compur branding. Synchro-Compur shutters have an additional lever painted green, which allows the user to select electronic flash synchronization ("X") or flashbulb sync ("M"). Some Compur shutters have a trailing -P, indicating these shutters offer "press to focus" functionality. A separate button is provided that allows the photographer to open the shutter leaves to check focus on the ground glass without changing the shutter speed setting or tripping the shutter. In the early 1970s, Deckel introduced electronically controlled shutters, branded as Compur-electronic. The 4.5 V PX21 battery required to operate these shutters is now out of production. ==Exposure value==

F. Deckel developed the exposure value (EV) scale, also known as the Light Value Scale, which is a single number that measures scene illumination on a base-2 logarithmic scale. Each EV corresponds to several combinations of shutter speed and aperture settings that provide the proper exposure for the illumination of the scene. The EV scale was first used on Synchro-Compur shutters displayed at Photokina 1954. ==Deckel-mount lenses==

File:Système Voigtländer, objectifs montés devant l'obturateur central.jpg|Voigtländer Ultramatic and dismounted lens File:Voigtländer-Lens Super-Dynarex-1-4-135-02.jpg|Voigtländer Super-Dynarex 135 mm lens, showing DKL-mount bayonet lugs File:Schneider Retina Xenon von Alf Sigaro.jpg|Schneider-Kreuznach Retina-Xenon 50 mm lens File:RetinaXenarDKL2.jpg|Schneider-Kreuznach Retina-Xenar 50 mm lens In the late 1950s, Deckel introduced a bayonet lens mount which was used mainly with 35mm leaf-shutter cameras built in Germany, including the Kodak Retina IIIS, Kodak Retina Reflex S, Braun Paxette Reflex, and Voigtländer Bessamatic. DKL-mount lenses for the Kodak cameras were made by both Schneider-Kreuznach and Rodenstock, while Voigtländer made their own lenses for the Bessamatic line. DKL-mount lenses became less popular as focal-plane shutter cameras became more prevalent in the 1960s, and production ceased by the early 1970s. The original bayonet was introduced in 1956 with the Voigtländer Vitessa T, followed by the Braun Colorette Super II in 1957, which shared the flange focal distance with the earlier Exakta system. Although the DKL-mount system is ostensibly compatible across manufacturers, camera manufacturers introduced variations in the mounting lug profiles and inclusion of an aperture control ring to physically prevent the attachment of lenses from other DKL-mount systems. For instance, the Schneider-Kreuznach and Rodenstock lenses made for the Kodak Retina S-mount do not fit Voigtländer cameras directly; a small physical modification to the mounting lugs will make them compatible. This was intended to prevent Voigtländer photographers from using less expensive Retina lenses. DKL lens mount cameras include seven distinct variants (the earliest models released, Voigtländer Vitessa T and Braun Colorette Super II, share the same physical mount): ;Notes ==References==