Digital special effects
- Created by: Alex Stephens
- Created on: 31-05-14 13:40
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- Digital special effects
- Compositing- blue screen and green screen
- It enables actors of scale models to be imposed on seperate filmed or computer-generated background.
- Used to create scenes that would be impossible or too dangerous to film or to impose actors in a computer-generated scene.
- The background and foreground are shot seperately as two pieces of film and then combined in a process called compositing.
- This is achieved using digital technology where the two films are digitised and the composite image made on a computer before being processed as a film.
- First, the background is filmed or created using computer-generated images (CGI) - this is called a background plate.
- Then the actor is filmed against a blue background or screen, which can be passed through a red filter to make it appear black.
- Silhouettes or mattes are created of the actor from the blue screen footage; one is black on a white background and the other is white in a black background.
- Four layers of film:
- Computer-generated background image- background plate
- Film footage of the actor in the foreground
- Matte- black silhouette on white background
- Matte- white silhouette on black background
- These four layers are combined to make a composite image. The black silhouette is placed on the background plate, creating a 'hole' into which the footage of the actor can be accurately placed.
- Four layers of film:
- Silhouettes or mattes are created of the actor from the blue screen footage; one is black on a white background and the other is white in a black background.
- Then the actor is filmed against a blue background or screen, which can be passed through a red filter to make it appear black.
- It enables actors of scale models to be imposed on seperate filmed or computer-generated background.
- The use of green screen has become dominant in film special effects. The main reason for this is that green emits more light than blue, making it easier to work with.
- Developments have also made it easier to incorprate motion into composited shots, where reference points are placed onto the blue background.
- Compositing- blue screen and green screen
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