Flash is the most popular artificial light source for both amateur photographers and professionals. It delivers a short, intense burst of light that can freeze moving subjects and illuminate objects up to a few metres away. Many cameras come with a built-in flash, but it’s also possible to add a more powerful and versatile external flash units to more advanced cameras. Flash is a complex area that gets a lot more interesting and a lot more complicated when you start using it for creative multi-light setups.