Kelly Calculator
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A Brief History of the Kelly Calculator As far as can be established, the first inkling of a pocket depth-of-field calculator that could be used instantly by a working motion-picture camera technician came about through the association of two distinguished British cinematographers during World War II. One, William Branch ‘Bill’ Pollard, born in Cambridge in 1914, was a documentary camera assistant and an ‘amateur’ mathematician (as he described himself); he gained an MA in Engineering Science at Cambridge University and studied further at the London Polytechnic School of Photography, the first cinematography school in Britain. The other was Graham White ‘Skeets’ Kelly, London-born in 1913, a well-established camera operator who had progressed through the ranks of the camera crew on major feature-films. At the start of the war, both men were inducted into the Royal Air Force Film Unit, based just outside London at Pinewood Studios – Bill as combat-camera assistant, and Skeets as a combat-cameraman. Thrown together, they were ‘routinely’ engaged in filming bomber raids over Germany and occupied Europe. |
| Given the distractions, nobody was keeping any detailed notes back then, but it is generally accepted by those who were around at the time that it was Pollard who first came up with the brilliant idea for a circular depth-of-field calculator, and that it was either both men or Kelly alone who then developed the concept to incorporate much more technical information on the other side of such a device. |
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In those days, any vital calculation was normally mined as needed from ‘the Jackson Rose', the American Cinematographer Hand Book and Reference Guide, compiled and written by veteran American cinematographer Jackson J Rose ASC, and first published by the association in the late Thirties. But when the Kelly Calculator hit the market in the early Fifties, it changed all that. While it didn't cover every base in detail like the venerated ASC manual, the ‘Kelly’ did offer depth-of-field scales for comprehensive range of lenses, as well as all the other information one might need during an average day's shooting. Faced with a scene that required some movie magic – perhaps a faster raw-stock with a ‘day-for-night' filter, plus using a non-standard shutter-setting while undercranking – ‘chain-calculations' presented the director of photography with no more of a problem than simply reading the answers off the Kelly's scales. Other scales dealt with variable filter, shutter, foot-candle and film-speed information compensated against basic aperture settings, and vice-versa; gauge-to-gauge, foot-to-metre, per-second footage and screen timers; screen-areas per screen-ratio; lens to distance to screen-size equivalents – all these available at a twist of a wrist on a flat, think feather-light calculator that usually sat in the camera assistant's hip-pocket ready for him, or anyone else, to use at a moment's notice. The Kelly even ended up in the kit of production designers, draughtspersons and script supervisors, and it sold all over the World. After fifty years, it still does, simply because nobody has ever come up with anything better.
After the war, Bill Pollard went on to enjoy a distinguished career as a documentary cameraman, receiving many awards and eventually becoming a Fellow of the British Kinematograph Society. Notably, in 1986, with fellow British cameraman and inventor, David Samuelson BSC, he shared an Academy Technical Award for his work on algorithms in depth-of-field calculations. Bill died peacefully at his home in Cambridge in May 1992, aged 78.
