The Williams process or Williams double matting process is a matte creation technique patented by the American cinematographer Frank D. Williams in 1918. Unlike prior matte techniques, it allowed for the integration of the actors' movements with previously shot backgrounds.
Due to this invention, Williams was able to found his own film lab, the Frank Williams Studio or Frank Williams Laboratories, devoted to the creation of all sorts of special effects (not just the Williams process) and where key figures of the special effects industry such as John P. Fulton worked.
In 1912 Frank Williams began working on his future invention under precarious conditions: he alternated periods of time working as a cameraman and saving money with others dedicated to working on his project, usually in the bathroom of wherever he was living in at the moment. His first attempt to use the William process was that same year, while he worked as a cameraman for the director Mack Sennet, but he did not succeed. The problem lay in the cameras and printers of the time as well as the film available, which made it impossible for it to work. However, Williams kept at it, and in 1917 he got help from the producer Adolph Zukor, who allowed Williams to work in his lab. Despite everything, the problems he had encountered in 1912 had not been solved and he failed again.
It was not until 1922, during the production of Wild Honey, that he succeeded thanks to the improvement of film quality and the use of tripods and a special printing machine. This printer, that Williams built himself, was accurate to a ten-thousandth of an inch and, according to the plans, cost 18,000 dollars.
The Williams process relies on the properties of the film. Firstly, the actors were filmed in front of a black background—although white or blue backgrounds were used later—and that was printed on high contrast film several times until a copy known as the holdout matte was achieved, which showed the black silhouette of the actors over a completely white background. That copy was inverted to make the cover matte, with the background black and the foreground white. Upon integrating the holdout matte and the desired background, the image was printed upon the white parts of the film while keeping the black silhouette untouched. Then, the original film was united with the new material, and, using the cover matte, it was printed upon the white parts, the white silhouette, to achieve the final copy.
For a long time, this was the only method available for creating moving mattes; but it presented some issues. The number of copies that had to be made caused a very difficult to deal with the halo effect. Moreover, though the process was suitable for color films, the results were not very convincing in black and white films.