Light Graffiti, London, United Kingdom

Light painting, also known as light drawing or light graffiti is a photographic technique in which exposures are made usually at night or in a darkened room by moving a hand-held light source or by moving the camera. In many cases the light source itself does not have to appear in the image. The term light painting also encompasses images lit from outside the frame with hand-held light sources. The first known photographer to use this technique was Man Ray in his series "Space Writing" created in 1935. The photographer Ellen Carey discovered Man Ray's signature signed by penlight nearly 74 years after the pictures had been taken.
Moving the light source
The light can either be used to selectively illuminate parts of the subject or to "paint" a picture by shining it directly into the camera lens. Light painting requires a sufficiently slow shutter speed, usually a second or more. Like night photography, it has grown in popularity since the advent of digital cameras because they allow photographers to see the results of their work immediately.