Thanks to the behind-the-scenes, extra footage found on many blockbuster Hollywood DVDs, we know the wonders of green- and bluescreen work on movies such as The Lord of the Rings trilogy, 300, Sky Captain and the World of Tomorrow, the Star Wars prequel trilogy, etc. Many of the scenes in these movies have layer upon layer of composites, such as painted backgrounds, live action footage and many layers of special effects - laser beams, explosions, robots, etc. But this is not only the domain of Hollywood studios with billion-dollar bank accounts. Robert Rodriguez is proud of the fact that he made many of the special effects in the Spy Kids series in his garage.

You know that typical split-screen/wipe when a character on screen calls another person? Viewers see the footage of a person answering their phone slide into the footage of the caller, usually from the right. This is compositing. Most such wipes are. There are many pre-made wipe transitions in editing programs, but you can also make your own by using your knowledge of compositing.

Remember that holographic SOS message sent by Princess Leia via R2D2 in Star Wars, Episode IV: A New Hope (1977)? We can easily do that today with compositing. Want ghosts in your story? No problem. All of these types of special effects can be done easily with compositing. How about an image of yourself talking to yourself? You could now be a triplet even.

We've arrived at the end of the article, and we haven't even talked about how to composite. The concept is fairly simple, but you can get as complex with it as your imagination allows. The main concept involves layers. You will need to work with two or more video layers on your timeline. Put some kind of static or moving image on video track #2 with some sort of transparency, and you will be able to see through to video layer #1. That is it, really.

There are all sorts of ways to do this. We have already mentioned alpha channels. Put a bug of your station's name, "Video Wizard Television," in the lower right corner of your frame by placing the logo with invisible alpha channel on video track #2 and this half-transparent gray logo will appear over any video you have on video track #1. Shoot an actor walking toward a camera against a greenscreen and "key out" or digitally erase the green background, drop the walking actor on video track #2 over footage of an exploding building on video track #1 and you have a giant Hollywood effect (where you get the footage of the exploding building is your real challenge - be careful). Cropping is also a useful tool, especially for the two-people-talking-on-the-phone example above. All the big editing programs allow you to crop a moving image.

This really is not as difficult as it seems. Figure out how your particular editing program handles alpha channels, key effects and cropping, and start making your own Hollywood effects or network television graphics.

Contributing Editor Morgan Paar is a nomadic producer, shooter and editor, currently teaching high school video production.