Long before "King Kong," "Star Wars," or "Titanic," inventor Thomas Edison took a baby step in the field of movie special effects. In a one-minute motion picture called "The Execution of Mary Queen of Scots," he had the leading lady's head chopped off. Or so it appeared.
Made in 1893, the shot was crafted using a technique that is still popular: stop-motion.
What Mr. Edison did was film a real actress and stop the camera. Then he replaced the real actress with a dummy and let the film roll again as an ax "beheaded" the fabricated stand-in.
A few years later, French magician Georges Melies (sometimes called the father of trick photography) began using this same principle after discovering that a jammed camera accidentally "morphed" a bus into a hearse.
Melies is also credited with a technique known as split-screen, in which half of the film frame is alternately masked (using a card or matte across the lens) during shooting. This concept can be used to have one person simultaneously play two parts, as occurs in Disney's "The Parent Trap."
In the current version of this film, moviemakers employ another popular tool: a blue screen (in this case, it's actually an illuminated blue screen). The blue screen is a more sophisticated way to combine two images on one frame of film. (A demonstration of how the blue- screen technique allows Lindsay Lohan to stand in front of herself can be found on "The Parent Trap" Web site: disney.com/DisneyPictures/ParentTrap/magic.html).
These are examples of visual or optical effects. Mechanical effects, which may enlist robots, puppets, and more, also are central to the special-effects trade.
The original 1933 "King Kong" combined miniature sets and stop-motion animation to make the scene of the ape scaling the Empire State Building.
Director Steven Spielberg reportedly was going to rely on stop-motion to make "Jurassic Park" until he was shown how dinosaurs could be "built" and animated using computers. That film made extensive use of computer-generated effects.