Sometimes the ambient light level is too low for successful for photography, or it’s the ‘wrong’ kind of light. This is where photographers turn to flash (or ‘strobe’, if you’re in the US). Flash works by emitting a very short, very powerful burst of light. Energy is stored in a capacitor in the flash head […]
Zoom head (flash)
More advanced flashguns have zoom heads which can use the zoom setting information sent to the camera to adjust their angle of coverage. If you're using a longer zoom setting, the angle of the flash narrows, which means that the light is more concentrated and the flash range is increased. It's a more efficient use of the flash power.