Battery–capacitor flash

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 photoflash 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 5.6 V, 15 V, or 22½ V batteries.

Polaroid BC flash model 281

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;^[1] the charged capacitor delivers a high-current pulse and reliably fires the bulb.