The problem with mattes is the camera had to stay perfectly still and no action could cross the matte line - the “hopefully” invisible line between the live action and the matte painting.
This is where the traveling matte came into place. The process patented by Frank Williams in 1918 and demonstrated here in F.W. Murnau’s 1927 film“Sunrise” - was a black matting process which photographed subjects against a pure black background. The film would then be copied to increasingly high contrast negatives until a black and white silhouette emerged. This black and white silhouette was used as the matte - called a traveling matte because it moved throughout the frame.
This “black back matte” effect which was called the Williams Process was used quite famously by John P. Fulton in 1933 for the film “The Invisble Man”. The shots where the invisible man was taking off his clothes were accomplished by photographing actor Claude Rains wearing a full black velvet suit standing against a black background. This effect was so memorable and startling it was used on follow up sequels even after more effective processes came along.
The Williams Process had some issues - for one, any shadows on the subject would be lost in the traveling matte. An alternative came about in 1925, invented C. Dodge Dunning which would eventually be called the Dunning Process.
This process used colored lights, lighting a background screen blue and the foreground subject in yellow. Using dyes and filters, the blue and yellow light could be split apart to create traveling mattes. The Dunning Process would first see use on King Kong in 1933.
The problem with the Dunning Process was it only worked with black and white film. Color Film needed a new technique and it would come in 1940 by special effects artist Larry Butler in the Thief of Bagdad.
Using the three strip technicolor process, Butler shot the subject against a blue background. Blue was used because it was the farthest away from skin tones and the blue film stock had the smallest grain. Taking the blue separation from the three technicolor negatives, Butler was able to create a silhouette matte just like with Williams process. Then, using an optical printer, a relatively new invention at the time that could combine multiple film strips into one, Butler would first remove the blue background from the foreground plate and, using the negative of the travelling matte, remove the foreground space from the background plate and then finally combining both foreground and background plates together.
This bluescreen technique won an Academy award for Best Special Effects for Lawrence Butler in 1940 but it was not without its inherent problems. Firstly the process was extremely time consuming as it involved several steps with an optical printer. Secondly, it still had some edge issues where a thin blue line was almost always visible in the shots. It also couldn’t handle any fine details like hair or smoke or motion blur. Despite these limitations, the blue screen process was used extensively including in such blockbusters as The Ten Commandments in 1956: