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Nick Flowers

Rotary Converter

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I was thinking that as the years roll on, those of us who used rotary converters to power the camera will be growing fewer and fewer, so perhaps it might not go amiss to set down what our jobs entailed. My first feature film was called 'Made', and we had a four man sound crew, of which I was the fourth man and pretty green too. My prime job was to set up and connect the camera (a Mitchell BNC) to a three phase power supply. If there wasn't a handy supply from the mains - in which case I would connect the camera via a transformer and a start box so the camera boys could turn over themselves - it would be my responsibility to connect the rotary. This derived its power from two twelve volt lorry batteries, which powered a 24 volt motor, which in turn rotated a three phase alternator. My memory fails me as what the voltage was between phases, but it was connected to the camera via four pin EP Canon plugs. The controls on the rotary converter were an on/off switch, a battery voltage meter, a meter for each output phase and a FRAM frequency meter, which consisted of about ten reeds, each cut to a critical length so that when vibrated by the common source the one which was vibrating the most would indicate the frequency of the supply reaching the camera - in Europe 50 Hz. On cold days it could take quite a few seconds for the rotary to get the camera up to speed and the clapper/loader could not put the board on until I shouted out "Speed", when the meter settled down at 50 Hz. There was another output from the rotary to allow a reference pulse from an ATN to feed into the Nagra. Rotaries and their batteries were not light weights and sometimes getting them in place involved a degree of physical exertion which I doubt I could summon today. We were much to be pitied. I expect I have forgotten quite a lot, and I used a rotary only on one film as Panavision cameras came into general use soon afterwards.

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During the period in which the "Barton Box", and later the Cinematography Electronics camera-speed control box was used to control film camera motors to adjust out the scan lines in early CRT computer monitors (an '80s thing), it would sometimes take a few seconds after film and sound (Nagra IV-S w/ TC, being fed field-rate by the Barton Box) to settle down into sync w/o the scan line.  I had an oscilloscope on my cart in those days so I could see when the pattern stabilized, and yell "speed"!

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