All of compositing involves the replacement of parts of an image with any other image or materials or when using video other video files or models are used. This is where blue and green screen come in handy as the compositing process takes away the designated colour and replaces it with the other image or footage required, most commonly seen during the weather forecast.
After doing a bit of research, we then had a seminar on this topic which was very helpful and gave even more detail on the subject which will be able to help me in my module even more as I will be compositing a lot of shots in my film.
History of Compositing
Compositing is a technique used to combine various shots into one images. It was first created by Georges Méliès in 1898 in his film, Four Head are Better than One, which used double exposure to create the effect of different layers. The technique uses glass which has been painted black to block out areas as other parts of the shot were exposed and then repeat this process but blocking other areas out instead. The Great Train Robbery was a film created in 1903, by Edwin S. Porter which used the same technique but he created larger and more realistic worlds that played in different layers to create the illusion that there was movement in the background.
Matte Paintings
One of the earliest examples of this was by Norman Dawn and this was a technique that again used the glass but they also include painting elements that were not originally in shot, for example The Raiders of the Lost Ark.
The paintings had to be ready on set but Norman Dawn got around this by using back matte and then re-exposing it over and over as many times as he needed to. This technique has been used since the 1900s and was used in many different films since then. The use of clear glass is a great technique as the actors could be in shot where the glass was clear but then where the glass had been painted the VFX artists could add in detail to make things look different without having to pay for them to actually be done in real life. For example if you had a run down house and during the film they made it look better this could be easily achieved using glass paintings as it does not cost a lot to print it out. The only downside is that the actor is then restricted to one area as if the actor goes anywhere behind the painting he will not be seen.
Traveling Matte
In 1918, Frank Williams patented the black matte process and this included a black background in each shot, in which figures would become bright white to due the high exposure they had to use. An example of this technique is the film Sunrise: A Song of Two Human 1927, in which they managed to get the actors to be walking while the background moved with them; groundbreaking technology for its time.
Blue Screen
Due to the major issues that they had with black screen, shadows getting lost in the background, the era of blue screen hit the industry. C. Dodge Dunning was the inventor of blue screen in which subjects where lit yellow, instead of the over-exposed white like before, and the background would be blue enabling a nice clean cut when compositing, in which the first film to use this was King Kong in 1933. But again the downside could only be used for black and white films, and colour was starting to become more affordable for smaller film companies.
In 1940 Larry Butler, who created the Butler Process saw the subject shot again, against a blue screen, but this time when processing he divided the shot up into what we now know as the RGB colour strip. He would use red, green and blue strips to separate the subject from the background and this could then create a better looking traveling matte for the subject and background combined. This was then used until 1950 as one of the best techniques until Petro Vlahos came into the picture.
"Yellow" Screen
Developed in the mid 50s, Petro Vlahos invented a new technique for film called the Sodium Vapor Process which was filmed in front of a white screen and then lit normally. But where this process differed from the previous ones is that he created a special camera that contained a sodium vapor prism inside it that emitted a light in a specific wavelength, which averaged at 589.3 nanometres a second. This specific camera created 4 strips, which consisted of the 3 RGB colours and then also a black and white one as well. The thing that makes this camera special, but I guess it's also the downside of this technique, is that only one was ever made, and that belonged to Disney, and they weren't all too keen about renting it out.
Return of the Blue Screen
In the late 50s people started to create more and more different types of cameras that all ran on different millimetres of film so a change had to be made and once again Petro Vlahos came into the picture. He spent 6 months developing the Colour Difference Matte Process which opened up clean edge compositing to everybody using any camera and any kind of film, and this process stuck until the 90s in which began the advent of digital compositing.
Blue Became Green
During the digtial age of compositing we got converted to green screen which wasn't as big of a change as it sounds. There were a lot more advantages to using green over blue in a way that its easier to light, it registers brighter on a digital display and it is a less common colour in clothing. Now that many digital cameras are used instead of the traditional film camera, they now ave sensors in them which use the Bayer Pattern, which is a grid that consists of the RGB scale. Due to the fact that green is seen more commonly on the pattern it was a lot easier to use this, but if required any colour can be used as a background nowadays providing that it is a solid colour.
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