A battery–capacitor flash (BC flash) is a
flash photography
A flash is a device used in photography that produces a brief burst of light (typically lasting 1/1000 to 1/200 of a second) at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a ...
system used with flashbulbs. Instead of relying directly on the current pulse ability of a
photoflash battery to directly fire a flashbulb, a battery is used to charge a
capacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
that is then discharged through the flashbulb. BC flash units use 5.6
V, 15 V, or 22½ V batteries.
Advantages
A special high-current photoflash battery is not needed, and even an ageing battery can charge the capacitor, although recycling more slowly than a fresh one;
the charged capacitor delivers a high-current pulse and reliably fires the bulb.
References
* Electronics for Photographers, by Marshall Lincoln, Copyright 1966 by Chilton Books, pp 43–54.
Capacitors & Batteries Boston University Physics Department
Flash photography
Photographic lighting
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