 | ||
A battery–capacitor flash (BC flash) is a flash photography system used with flashbulbs. Instead of relying directly on the current pulse ability of a battery to directly fire a flashbulb, a battery is used to charge a capacitor that is then discharged through the flashbulb. BC flash units use 5.6V, 15V, or 22½V batteries.
Advantages
The advantage is that even with an aging battery, the flashbulb still gets a high current pulse and thus reliably fires, although the recycle time between flashes increases as the battery ages.
References
Battery–capacitor flash Wikipedia(Text) CC BY-SA