Green screening
Green screening is a form of Chroma key compositing where a green background is used and required images are layered onto it. The required images replace the part of the screen which is green. It is commonly used in weather broadcasts where a presenter stands in front of a green screen which is then replaced with the required map. It is also used extensively in film and television, allowing action to take place in any location even a fantasy one!
History
The Blue screen method was first developed at RKO pictures in the1930's. Initially bluescreens were used to create 'travelling mattes', first used for screen wipes at a change of scene. The first proper use was credited to their of bagdad in 1940, but even before this they had been using layering and mattes to build up images in cinema. Originally this technique could only be used effectively for very static shots. Later a technique was developed using an optical printer, two projectors, a camera and a beam splitter. The footage was then combined one frame at a time. Gradually from the early 1970's there was a move from blue to green screen and microcomputers were used to speed up the process. This was first used for Empire Sprikes back in 1981. AS time have gone on and computer technology has developed, the use of Green screen has become the industry standard. It is now possible to incorporate motion into composted shots making use of reference points on the mattes.
Green screen was used in Avengers to put the actors against the explosions and impose them onto a New York City both a CGI New York City and the real life New York City. It was done for practicality , its expensive to film in New York and you can't really put massive explosions in a real city and also there could be no harm to the actors so no one could get hurt yet it seemed like they were in the explosion. The final images look very convincing and work well in the film.
Mattes and Matte Painitng
A matte painting is a tool of film makers which the use to show backgrounds which are not real or to expensive to film. These are landscapes which are often painted on glass. It also allows you to give buildings and sets extra flair when the expense of building the entire set would be too costly. In these scenes the painting is static and the movement is done set infront of the matte. These look seamless at best but is dependant on the skill of the artist and it has the potential to be more visually stunning than cgi and probably cheaper.
History
Mattes and Matte Painting started out in 1907 when it was first used in Missions of California to portray the crumbling Californian mission. It continued being used through the 20th Century notably in films like Wizard of Oz (the emerald city), Starwars Episode IV to portray the seemingly bottomless tractor beam set. In the mid 1980's Mattes started moving to the digital realm for films like Young sherlock homes. Then more films started using the technique. By the 1990's the use of digital became standard in film. James Camerons Titanic was one of the last to use Matte painted on glass for the Carpathia rescue ship. Now Matte Paining is effectively all digital with 3D mattes made with different lighting algorithms inside the computer made with tablets.
Matte Painting was used to Iconic effect in the final scene of raiders to show a impossibly massive warehouse of artefacts where the ark of the covenant was to be stored. The scene is highly effective you see movement in the foreground as the ark is moved to storage.
Rotoscoping
Rotoscoping is an animation process where they project a frame of live image and the then trace over the top. Originally this was done by projecting an image on frosted glass, then the animator could trace the general movement. The projecting device was called a rotoscope. The name rotoscoping is used for the technique that is still used in the digital era.
History
Max Fleischer invented the rotoscope and used it in his ground breaking out of the ink well series, Walt Disney used the technique to great effect in his animated movies from snow white and beyond to give realistic movement of humans and animals. Although largely used to bring realism to high budget animated films, Filmation perfected the technique in there low budget animations using repetitions of certain moments in Animations such as He Man and the masters of the universe.One classic use of rotoscoping as an after effect was in the original three Starwars movies was to create the glowing light sabres by matting over a stick that was being held by the actors using a rotoscope, give the glowing light sabre effect. Rotoscoping often called a Roto is still used today along side other processes it is part of creating and removing or replacing a digital matte and often used with motion capture.
In A Scanner Darkly, the effect can be seen as you can see the leading actors animations, these are quite famous actors and its easy to see how the rotoscoping technique has been used to draw them. They seem to be quite effective and there movement looks real. As you can see below with Keanu Reeves and Robert Downey Junior.
And also rotoscoping was used very effectively in the Aha music video take on me. https://www.youtube.com/watch?v=djV11Xbc914
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