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It's All in How You Look at It, Part 4

© Elizabeth Burton

The grandfather of all special effects techniques is without question the venerable blue-screen process. Though largely replaced by fancy computer-generated images, this simple process of combining images from two strips of film was the basis for some of our most memorable movie images.

• ET soaring across the face of the full moon on the handlebars of a bicycle.
• Dorothy watching as the mean Miss Gooch transforms into the Wicked Witch of the West in the middle of a tornado.
• Claude Rains unwrapping his bandages and disappearing
• The magnificent backdrop of Gotham City

The original blue-screen process -- also known as the “traveling matte” process for reasons I’ll explain in a bit -- basically involves creating a sort of movie collage. Unlike the sodium-vapor process discussed in the last article, blue-screen uses only a single camera. First, the actors are filmed in white light performing in front of a blue screen with a color negative. Why blue? Because human skin tones rarely contain blue pigment. If models are used, or the performers are wearing colorful costumes, almost any color screen will do.¹

This negative is then run through a series of printing processes using various color filters to create a matte, or mask. In this case, the matte is known as a female matte or matte master, where the foreground action is clear and the background is opaque.

From this matte, a second one is made in which the images are reversed: the background is clear and the foreground is opaque. Because the actors’ positions change from frame to frame, these are also known as traveling mattes.

Before computers, these two positives were then run through an optical printer, which is a combination projector/camera unit specially designed to work with pre-prepared film. First, the male, background matte was projected onto a new negative, then the process was repeated with the female, foreground matte creating a composite image. Today, computers allow the images to be manipulated digitally.²

If you’d like to experiment with some simple special effects of your own, consider starting with the static matte process. Basically nothing more than creating a double exposure by masking out part of the camera lens, shooting a scene, then filming again with the same negative but with the previously exposed portion of the lens covered.

Matte paintings can enhance the look of a movie, allowing filmmakers to create cities that don’t exist or reproduce distant locales without having to go there. In Batman, Tim Burton used ust such a painting on glass to supplement a backlot city street and create the brooding, gothic atmosphere of Gotham City. The magnificent Emerald City in The Wizard of Oz, rising up on the far side of the field of poppies, is also a matte painting.

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