Ring flash is a specialized type of circular lighting tube that surrounds a lens and consequently produces shadowless light. Its principal application is for close-up work where a lens is placed within one or two metres of a subject. Since the lens is surrounded by a column of light, no shadows are generated and contrast in the image is reduced. Ring-flash puts distinctive annular highlights in reflective objects such as droplets of water and eyes. Since they are designed principally for close-up work, ring-flash units tend to be less powerful than conventional flashguns.