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Sridhar Kumar

HMI Lighting and Crystal cameras

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In one of the book I am reading, it says "Most of them (HMI Lighting) run on 240 volts and can be used only with crystal cameras."

 

I didn't get any clear information on crystal cameras in google search. What does crystal camera mean?

 

Thanks.

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Probably a reference to a type of motor used on film cameras starting back in the 1970's.

Precision speed control was achieved using crystal-controlled electronics. The main advantage

was the ability to record synchronous sound without the need for cable connections between

camera and recorder, but it would also provide extremely accurate, constant exposure from frame

to frame.

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Incidentally, your book is incorrect. Non- crystal motors run at a steady enough speed to avoid flicker with HMI, assuming the right shutter angle is used. The main point of crystal control wasn't speed accuracy but cable-free sync.

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120 and 230v synchronous motors which take their constant speed from the mains grid frequency have been around much longer (at least from the 40's) than the battery powered crystal motors where the speed reference is generated internally

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I for example have an old Cameflex mains powered motor from the 40's which runs perfectly 25.00fps. it is actually possible to use an inverter to get 230v 50Hz input to it and thus get it running steadily at 25.00 fps with battery power

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