Datenbank Glossar – Special Effects

Matte painting

Mattes are used in photography and special effects filmmaking to combine two or more image elements into a single, final image.

A landscape, set, or distant location that allows filmmakers to create the illusion of an environment that would otherwise be too expensive to build

The matte is the background painting. In film and stage, mattes can be physically huge sections of painted canvas, portraying large scenic expanses of landscapes.

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, and layering mattes on top of one another.

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 and sky 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.

Photo shop matte painting tutorial :

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Rotoscoping

Rotoscoping is an animation technique in which animators trace over live-action film movement, frame by frame, for use in animated films. Originally, pre-recorded live-action film images were projected onto a frosted glass panel and re-drawn by an animator. This projection equipment is called a rotoscope, although this device has been replaced by computers in recent years. In the visual effects industry, the term rotoscoping refers to the technique of manually creating a matte for an element on a live-action plate so it may be composited over another background.

Rotoscoping (often abbreviated as “roto”) has often been used as a tool for visual effects in live-action movies. By tracing an object, a silhouette (called a matte) is created that can be used to extract that object from a scene for use on a different background. While blue and green screen techniques have made the process of layering subjects in scenes easier, rotoscoping still plays a large role in the production of visual effects imagery. Rotoscoping in the digital domain is often aided by motion tracking and onion-skinning software. Rotoscoping is often used in the preparation of garbage mattes for other matte-pulling processes.

Rotoscoping has also been used to allow a special visual effect (such as a glow, for example) to be guided by the matte or rotoscoped line. One classic use of traditional rotoscoping was in the original three Star Wars films, where it was used to create the glowing lightsaber effect, by creating a matte based on sticks held by the actors. To achieve this, editors traced a line over each frame with the prop, then enlarged each line and digitally added the glow.

Reference – Art of Roto :

http://www.fxguide.com/fxtips-243.html

Vertigo

A dolly zoom in the film Goodfellas. Notice the significant change in background.

This animation shows a dolly zoom being performed. At the top of the image we see the camera’s view; the cubes stay the same size as the teapots in the background grow bigger. At the bottom of the image is a plan view showing the camera moving back while zooming in, illustrating how the effect is achieved.The dolly zoom is an unsettling in-camera special effect that appears to undermine normal visual perception in film.

The effect is achieved by using the setting of a zoom lens to adjust the angle of view (often referred to as field of view) while the camera dollies (or moves) towards or away from the subject in such a way as to keep the subject the same size in the frame throughout. In its classic form, the camera is pulled away from a subject whilst the lens zooms in, or vice-versa. Thus, during the zoom, there is a continuous perspective distortion, the most directly noticeable feature being that the background appears to change size relative to the subject.

As the human visual system uses both size and perspective cues to judge the relative sizes of objects, seeing a perspective change without a size change is a highly unsettling effect, and the emotional impact of this effect is greater than the description above can suggest. The visual appearance for the viewer is that either the background suddenly grows in size and detail overwhelming the foreground; or the foreground becomes immense and dominates its previous setting, depending on which way the dolly zoom is executed.

The effect was first developed by Irmin Roberts, a Paramount second-unit cameraman, and was famously used by Alfred Hitchcock in his film Vertigo