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. Light Painting Photography can be traced back to the year 1914 when Frank Gilbreth, along with his wife Lillian Moller Gilbreth, used small lights and the open shutter of a camera to track the motion of manufacturing and clerical workers. The Gilbreth’s did not create the photographs as an artistic endeavor; they instead were studying what they called “work simplification”. The Gilbreth’s were working on developing ways to increase employee output and simplify their jobs. While they were not using light painting as an artistic medium they did produce the first known light painting photographs. 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.