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 […]
Guide Number (GN)
A measure of the power of a flashgun, whether it’s a built in flash or an external flashgun. You take the guide number and divide it by the subject distance in metres to get the lens aperture you should use. Flash power is usually controlled automatically these days, though, so the guide number is just an indication of the maximum power.