Dawn’s first film Missions of California made extensive use of the glass shot, in which certain things are painted on a piece of glass and placed in between the camera and the live action. Many of the buildings which Dawn was filming were at least partially destroyed; by painting sections of roof or walls, the impression was made that the buildings were in fact, whole. The main difference between the glass shot and the matte shot is that with a glass shot, all filming is done with a single exposure of film.
Dawn combined his experience with the glass shot with the techniques of the matte shot. Up until this time, the matte shot was essentially a double-exposure: a section of the camera’s field would be blocked with a piece of cardboard to block the exposure, the film would be rewound, and the blocked part would also be shot in live action. Dawn instead used pieces of glass with sections painted black (which was more effective at absorbing light than cardboard), and transferred the film to a second, stationary camera rather than merely rewinding the film. The matte painting was then drawn to exactly match the proportion and perspective to the live action shot. The low cost and high quality of Dawn’s matte shot made it the mainstay in special effects cinema throughout the century.
Dawn patented his invention on 11 June 1918 and sued for infringement of the patent three years later. The co-defendants, matte artists who included Ferdinand Pinney Earle, counter-sued, claiming that the technique of masking images and double exposure had long been traditional in the industry, a legal battle which Dawn ultimately lost