So far, we've focused on the trailer as an extension of the film, measuring it as an advertising tool, a PR device, and an introductory prologue. But what about the trailer in and of itself? There's something to be said for the technique and artistry that goes into constructing an exhilarating 2 1/2-minute piece of film, regardless of its impact on box-office results or popular opinion.

Some of the coolest trailers ever made announced movies that either bombed or left audiences terribly disappointed: Robin Williams delivering a stand-up riff in the middle of an open field for Toys, Ralph Fiennes hypnotically pitching virtual-reality trips for Strange Days, Gabriel Bryne elegantly sketching a cartoon bombshell for Cool World. Whether or not a film succeeds at the box office says nothing for its merits as a piece of entertainment in its own right.

Like the movies themselves, previews are produced through a collaborative effort. From the lowliest editor or copywriter to the director, stars and studio advertising heads, everyone has some say in the process. In most cases, the men and women who edit previews are aspiring filmmakers themselves. "We all went to film school with the hope of doing something artistic," says Dan Asma, a trailer editor for CBO, "And there are times when we can be artistic. Nine times out of 10, we're selling something." Every once in a while, they sneak a great idea past the market researchers and studio gatekeepers, but as Intralink president Anthony Goldschmidt says, "The best work generally has not been seen."

On certain rare occasions, the crew working on the trailers will come up with an idea that impresses the filmmakers enough to alter (or at least influence) the film, from simple music cues and editing feats to the adoption of entire sequences shot specially for the preview. "Our choices in music have influenced pictures," explains Kaleidoscope's Andrew Kuehn. "With Titanic, we started using Enya for the first cuts of the trailer, and then Cameron tried to strike a deal there. They wanted to write the whole score, he just wanted to use the song, and that fell through." Both the arrow's-eye point of view shot from Robin Hood: Prince of Thieves and the "search every hen house and chicken coop in a five-mile radius" speech from The Fugitive originated at The Seiniger Advertising Group, where the creative staff generated new material to help the trailer pack more punch.

"As an editor, you get one complete cut," explains CBO's Phil Terrence. Every editor chases fantasies that the studio will green-light his original cut for a trailer. Some have actually seen it happen. As Kuehn tells it, after showing Universal president Sid Shineberg his first cut of the Jaws 2 trailer, for which he wrote the unforgettable line of copy, "Just when you thought it was safe to go back in the water," Shineberg asked incredulously, "Do we have that picture? ... Don't anybody touch this trailer! Send this to the exhibitors in the black and white form." However, most editors are accustomed to the reality of the process, where the studio shoots down the innovative ideas (often for good, practical reasons: because they don't sell the film) and demands 150 revisions before finally accepting the completed trailer.

In the end, previews represent the imaginations and talents of not only those who participated in making the film, but also (and especially) the creative minds responsible for constructing the 2 1/2-minute work of art designed to sell the movie to audiences. Previews emerge either so finely tuned or grossly disfigured that they demand we evaluate them on their own terms, independent of the films themselves.

There are those who might even argue that the heartrending four-and-a-half-minute trailer for Titanic, abbreviated to the film's most dramatic moments, comes across just as powerfully as the finished picture. Some of the most exciting aspects of modern art have been channeled into advertising, a realm where visionary artists can make a decent living. If you ask me, Ridley Scott's 1984 SuperBowl television spot for Apple computers deserves to be recognized for the same artistic audacity critics and fans applaud him for with Blade Runner.

"People try to do something 'special,' but if it's not integral to the movie, or the concept is not organic, it will usually fail as a piece of advertising," says David Sameth, who produced the American Beauty trailer for DreamWorks. "There are a lot of standard trailers. There are only so many movies a year that can have the raw material for brilliance."

Advertisers get really excited when film critics describe a movie as "an edge-of-your-seat thrill ride" because quotations like that look great in newspaper ads, whether or not any two-hour feature can ever live up to such a description. But reduced to a more manageable bite, movies can and do inspire strong emotional reactions. Trailers drastically condense and accelerate the excitement of a full-length film for maximum impact, and audiences respond. They laugh. They cry. They cheer. Whether sitting silently riveted to the screen or vocally expressing their satisfaction, moviegoers love a great trailer.