C-mount lenses have been enjoying a period of popularity with still photographers over the last couple of years due to their use with an adapter on the new micro 4/3rds format. Some photographers have also been trying them out on the Sony NEX cameras and it is likely that with the launch on the market of the upcoming Scarlet 2/3 Cinema (interchangeable lens) digital film camera, their popularity is only due to increase. But the C-mount standard has been around for a long time and an interesting history: let’s take a look!
16mm film is invented
C-mount lenses were first used for early cine cameras: the “c” in the name probably stands for “cine”. The earliest beginnings are a little vague. The c-mount standard is for a 1″ diameter screw mount with a 32 thread per inch pitch and a 17.526 millimetres (0.6900 in) flange focal distance. It does not refer to the coverage of the lens, but it was almost certainly established for use with 16mm film. This was introduced to the market by Eastman Kodak in 1923. Prior to this, the main format used was 35mm. Up until the early 1920s, 35mm film was a negative stock that had to be printed to be projected, was made of an inflammable nitrate base, and was altogether too large, dangerous and costly for amateur home use. The new 16mm film was a reversal film that needed no printing, was cellulose acetate based “Safety Film” and cost much less, opening the path for a new amateur market. The same year, Bell & Howell introduced the first model of its famous Filmo camera, the Filmo 70A. Placing ads in popular nationwide US magazines, Bell & Howell marketed the Filmo to home movie makers for the first time. Costing $180, the Filmo was certainly not within the reach of everyone, but amongst the wealthy a new hobby was born (the cheaper 8mm format, which further encouraged film making as a hobby, arrived in 1932).
The Bell & Howell Filmo 70 Camera
The Filmo 70A was a single lens camera which probably had a C-mount. What is certain is that it’s 1927 successor, the Filmo 70C, had a three lens revolving turret which mounted three c-mount lenses of varying focal length. Bell & Howell also made a kit for retrofitting the turret to the the 70A and the 70B (a high-speed scientific version similar to the 70A). All the early Filmo 70 cameras were fitted with lenses made by Cooke of England. A 1″ f3.5 universal focus anastigmat was sold as the standard focal length, but the Cooke range stretched from a 2/3″ f2.5 “wide” to a 6″ f5.5 “tele”. It seems likely that this was the first range of c-mount lenses.
The 16mm format was a success: by the late 1920s many manufacturers had introduced their own model, while famous lens makers like Cooke, Dallmeyer, Kern, Hugo Meyer, C.P. Goerz, Wollensak, Schneider Optics and others were making c-mount lenses to equip them. Rather than an amateur format, 16mm ended up being used for news gathering, reportage and small budget productions. The Filmo 70 itself became the most famous news gathering camera of all time, landing with Allied troops on the Normandy beaches, covering the action during the Vietnam conflict and being adopted by the early TV studios when they started sending out reporters to get live footage.
The Vidicon Tube
Not all early c-mount lenses were made for 16mm film but most of them were. Some were also made for 8mm film, although this format generally used the smaller diameter D-mount. From the 1950s, however, the situation became more complicated because C-mount lenses began to be used not only for film, but also for early TV cameras and then for industrial and CCTV cameras. The earliest TV cameras used very large video camera tubes or pickup tubes. The coverage required was very large and so were the cameras and lenses: c-mount lenses were not suitable. In the early 1950s RCA developed the smaller Vidicon tubes. Typically of 1″ or 2/3″ diameter*, these could be used in much smaller, portable cameras which could mount new and existing c-mount lenses. At the beginning, it was probably existing lenses and designs that were used. Many of the earlier TV lenses seem to be of much higher quality than later ones. The Canon TV-16 series of lenses, for example, is so named because they were designed for both 16mm film use and for TV – hence the name “TV-16”. The early c-mount Cosmicar lenses were marketed as a TV lens, but exactly the same lenses were also marketed for 16mm use under the name Kinotar Professional.
The TV cameras didn’t require the same resolution in a lens as 16mm film however, and as time went by lenses started to be made specifically for use on TV cameras. Many of these were zooms, typically in the 12.5-75mm or 16-100mm range, and they often boasted wide maximum apertures to capture as much light as possible. In the meantime, c-mount zoom lenses had also been developed for the 16mm film cameras. The earliest of these, like the Som Berthiot Pan Cinor 20-80mm f2.8, came with a parallax corrected viewfinder, but by the late 1950s and early 1960s, Som Berthiot and Angenieux were producing zoom lenses with an integrated viewfinder offering through-the-lens viewing. The introduction of the Bolex H-16 Reflex camera with it’s own prism viewing system brought with it new lenses optically corrected for this camera, the RX c-mount lenses (a separate article on this will be published on this site shortly).
The CCD Sensor
The use of c-mount lenses on TV or video cameras lasted for about thirty years – from the 1950s to the 1980s. Then the Vidicon tube was supplanted by the CCD sensor. The market for video cameras split into a lower end with fixed zoom lenses and a higher professional end with larger interchangeable zoom lenses, using bayonet mounts, that were optically designed for use with 3 ccds behind a beam splitter prism. Bayonet mounts were introduced into the world of 16mm and Super 16 film as well: today, the majority of new cine lenses are fitted with the Arri PL mount.
Although a few cine lenses are still produced in c-mount today, by far the largest part of the market for new c-mount lenses is for CCTV and industrial lenses. The sensor sizes these are designed for differ enormously: many are for 1/4″ or 1/3″ sensors while others are designed to cover 1/2″, 2/3″, 1″ or even (rarely) 22mm. Quality of these lenses differs hugely too: at one end of the scale are cheap, plastic lenses, sometimes with a fixed focus or aperture, while at the other end there are quality, precision lenses offering high resolution and solid build designed for various applications from quality control to scientific research.
However, with Micro 4/3, NEX and Silicon Imaging’s SI-2K already on the market and with the Red Scarlet and Ikonoskop A-Cam dII Interchangeable lens cameras due to join them, we are already beginning to see new C-Mount lenses designed for photographic and cine use. The number only seems likely to grow.
* A lot of confusion exists on the exact meanings of formats and sensor size – a separate article will come on this soon.
Links and References
The history of the B&H Filmo Camera http://www.tfgtransfer.com/filmo.htm
List of manufacturers of vintage cinematographic equipment http://www.xs4all.nl/~wichm/cinelist.html#B&H
The Bolex Collector http://www.bolexcollector.com
LabGuy’s World: The History of Video Tape Recorders before Betamax and VHS http://www.labguysworld.com/index.html