Have you ever seen the 1933 movie King Kong? It is one of the most memorable examples of early experiments with special effects. King Kong himself was an animated model, brought to life on screen using stop-motion filming. It is a very labor-intensive method: models have to be moved a fraction of an inch, their facial expressions changed, and then shot, with 24 different shots being taken for just one second of film.

• See how to make your own flipbook animation, which mimics the effect of stop-motion filming, at Cosmikanga. Here's a more advanced version, making flipbook animations with photographs, from the Rochester Institute of Technology.

King Kong's costar in the movie was the actress Fay Wray. If Kong was an animated model, how did the early filmmakers make it look as though he was interacting with an actress? The answer lies in a technique known as "optical printing." The producers filmed Kong and Fay Wray separately. They then projected the two films together and used another camera to record the information on a third reel of film. The result: on film, it looks as though Fay Wray is right there with Kong. The separate elements — animation, scenery, and human characters — were merged to appear as though they all existed together during filming. The scene appears real. This blending of shots is now known as compositing. It's still done today, but using different methods.

• Read a biography of Linwood G. Dunn and find out about his role in designing the first manufactured optical printer.
• You can also visit the masters of stop-motion animation, Aardman Studios. They created Wallace and Gromit and will soon release 12 new one-minute episodes exclusively on the Web.

One important tool in digital compositing is the "blue screen." Movie stars perform a scene in a studio, in front of a blue screen. Later, computer programs are used to replace the blue background with a real background, such as an ocean scene. So, even though the actor was filmed in a studio, it will look like he was filmed out at sea.

The blue screen was used several times in the movie Forrest Gump. In one of the most memorable scenes, actor Tom Hanks appears to shake hands with President John F. Kennedy — who in reality passed away over 35 years before the movie was made. The movie producers filmed Hanks in front of a blue screen, pretending he was interacting with the President. They then used computer technology to isolate Hanks and insert him into an old film clip featuring President Kennedy.

• Create your own blue screen special effects with step-by-step instruction from the Cyber Film School.
• Learn more about the history and terminology of special effects at the Nova Web site on special effects and the HowStuffWorks Web site.
• Consider the last three "great" movies you saw. How important do you think special effects were to your enjoyment of those movies?

The Nickelodeon movie Clockstoppers, which will be released on March 29th, uses the technique known as "time-slicing." It was important for the Clockstoppers plot that objects appear to be frozen in time. In the movie, the camera seems to rotate around objects, giving you a three-dimensional view of them as they stand still. In fact, a ring of cameras is positioned around the object, and the cameras all take a still image at the same time. When the images are played together, it looks as though there is one camera moving around the object, caught in one moment of time.

Computer animation has taken on a life of its own, too. Sometimes, animated characters interact with real scenes and humans on screen: in The Lord of the Rings, many of the creatures Frodo and Samwise encountered — such as the Cave Troll in the Mines of Moria — were computer-animated. Flubber starred computer-animated goo alongside actor Robin Williams. In another Williams movie, Jumanji, the jungle animals that trampled through town — destroying everything in their path — weren't real.

The biggest news in computer animation is this year's new Oscar category of "Animated Feature Film." The three contenders are Monsters Inc., Shrek, and Jimmy Neutron: Boy Genius. The much-admired detail of these movies (think of Sulley's furry coat in Monsters Inc.) would have been painstaking to create in old hand-drawn animations, but today's powerful computers make it possible to make animated characters seem very real.

• Visit the official Web site of the new computer-animated movie, Ice Age, which is doing well at the box office right now.
• Learn more about special effects used in the movie Flubber from the Visual Effects Headquarters.
• How is computer animation affecting workers in the movie making industry? Find out in "21st Century Movies" on PBS' OnlineNewsHour.
• Read a review of The Perfect Storm by famous film critic Roger Ebert. Do you agree with his take on the movie? Why or why not?
• Consider the last movie you saw which had special effects. Write a review of the movie based on the realism and impact of the special effects. Support your claims with specific examples from the movie. Here are some questions to consider:
  • Were the special effects believable?
  • Did the special effects enhance the movie?
  • How could the special effects have been improved?

The Price of Effects
Movie budgets continue to rise as movie producers create more impressive visual effects to lure you to the theater. If a movie is successful, it earns more money than it costs to produce, thus yielding a profit. However, in some cases, the cost of the movie outweighs the money it takes in at the box office.

• Look at the data below figure out which movie earned the highest percentage profit and which movie had the largest percentage loss.

• Are you willing to pay higher movie ticket prices to fund state-of-the-art movie theaters and more expensive special effects?

— by Zora Warren of the Harvard Graduate School of Education's "Technology in Education" program