History of Compositing

Compositing is a technique employed to combine different shots and elements into one Image. In the 1898 film 'Melies' the director, Georges Melies used a double exposure technique to create the shots, parts of the exposure was blocked using black paint on a piece of glass, the film was then rewound and a new matte matte would expose the previously blocked areas and block the already exposed ares. This is called 'Un Homme De Tetes'.

This tecnique was also used by Edwin S. Porter in the 1903 film 'The Great Train Robbery' however Porter used it to create a larger more realistic world.

As film production developed as did the techniques for compositing, the 'Glass Shot' was developed by Norman Dawn, which was simply a plate of glass with elements painted on and placed between the camera and the subject, the problem with this however it that the camera could not be moved, and also had to be ready on set, however Dawn got round this by creating a black matte with the glass and then re-exposing the film when the artists had finished the painting. 


Frank Williams furthered this process by using a black background which the subject was filmed on and then increasingly high contrast negatives were copied until only the silhouette remained. This was known as the 'Travelling Matte'.



However the problem with this process was that in the black matte all the shadows would be lost. So in 1925 Dodge Dunning developed a process that delt with the issue, the 'Dunning Process' used coloured lights to identify  a subject from the background, creating separation. This is called the 'Blue Screen'.

This was however only used in black and white film as the lights had to be coloured yellow, and as more colour was coming into films a new technique took over. 

In 1940 Larry Butler created a process that allowed this, the 'Butler Process' used the subject shot against blue background, using Technicolor film. this needed an optical printer to remove the need of multiple exposure.  Shot using the three strip process the blue channel could be used to separate the subject from the background and to create a travelling matte for the background. 

This remained as the best compositing technique until the late 1950's when Petro Vlahos invented the 'Sodium Vapour Process'. This process allowed actors, standing in front of a white screen, to be lit normally while the screen was lit by powerful sodium vapour lights. As the lights emit a very specific wavelength, that averages out to 589.3 nm/s Valhos was able to design a special camera that could separate the sodium vapour lit background from the subject. A specially coated prism in a converted film camera split off the sodium light and captured it onto a black and white film while the normal light was captured to regular 3 strip film. 

However as only one camera was made and owned by disney it was rarely rented and when it was it wasn't cheap. Most compeines reverted to the Blue screen tecnique and Vlahos spent 6  months improving the blue screen process and developed it into the 'Colour Difference Matte Process'. This created a clean mask with minimal edge. This remaind the prime tecnique for over 40 years. It was hardly changed until digital compositing was created. As Green registers brighter on electronic displays, and it was a less common colour of clothing as well as being easier to light, it became more and more popular. Most digital camera sensors capture double the amount of green as they do blue or red, making green easier to key.