Matte (filmmaking)
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Mattes are used in photography and special effects filmmaking to combine two or more image elements into a single, final image. Usually, mattes are used to combine a foreground image (such as actors on a set, or a spaceship) with a background image (a scenic vista, a field of stars and planets).
In film, the principle of a matte requires masking certain areas of the film emulsion to selectively control which areas are exposed. However, many complex special-effects scenes have included dozens of discrete image elements, requiring very complex use of mattes.
For an example of a simple matte, we may wish to depict a group of actors in front of a store, with a massive city visible above the store's roof. We would have two images-- the actors on the set, and the image of the city-- to combine onto a third. This would require two masks/mattes. One would mask everything above the store's roof, and the other would mask everything below it. By using these masks/mattes when copying these images onto the third, we can combine the images without creating ghostly double-exposures. In film, this is an example of a static matte, where the shape of the mask does not change from frame to frame.
Other shots may require mattes that change, to mask the shapes of moving objects such as human beings or spaceships. These are known as travelling mattes. Travelling mattes enable greater freedom of composition and movement, but they are also more difficult to accomplish. Bluescreen techniques, originally invented by Petro Vlahos, are probably the best known techniques for creating travelling mattes, although rotoscoping and multiple motion control passes have also been used in the past.
[edit] Mattes and widescreen filming
Another use of mattes in filmmaking is to create a widescreen effect. In this process, the top and bottom of a standard frame are matted out, or masked, with black bars, i.e. the film print has a thick frame line. Then the frame within the full frame is enlarged to fill a screen when projected in a theater.
Thus, in "masked widescreen" an image with an aspect ratio of 1.85:1 is created by using a standard, 1.33:1 frame and matting out the top and bottom. If the image is matted during the filming process it is called a "hard matte." In contrast, if the full frame is filled during filming and the projectionist is relied upon to matte out the top and bottom in the theater, it is referred to as a "soft matte."
In video, a similar effect is often used to present widescreen films on a conventional, 1.33:1 television screen. In this case, the process is called letterboxing. For video transfers, transferring a "soft matte" film to a home video format with the full frame exposed, thus removing the mattes at the top and bottom, is referred to as an "open matte transfer." In contrast, transferring a "soft matte" film to a home video format with the theatrical mattes intact is referred to as a "closed matte transfer."
[edit] Garbage matte
A "garbage matte" is often hand-drawn, sometimes very quickly made, and can be used to exclude parts of an image that a procedural process, such as bluescreen, would not remove. The name stems from the fact that the matte removes "garbage" from the procedurally produced image. This "garbage" might include a rig that is holding a model or the lighting grid above the top edge of the bluescreen. Garbage mattes can also be used to include parts of the image that might otherwise have been removed by the bluescreen, such as too much blue reflecting on a shiny model ("blue spill").
[edit] See also
- Alpha compositing
- Anamorphic format
- Bipack
- Compositing
- Difference matte
- Gash matte
- In-camera effect
- Schüfftan process
- Widescreen
