In the 1970s, when chromakey technology debuted, it was mainly used in television newsrooms, to project images into a monitor behind the local weatherman, allowing him to interact with animated maps, graphics, and scenes of the local community.
In that role, chromakey did its job reasonably well, but when first used by Hollywood for television special effects, it almost always looked cheap and hokey (four simple words: Land of the Lost.)
But in the decades since, chromakey has shed many of its negative connotations. Combined with computers, sophisticated software and high-definition video, it's the first step to giving films such as Sky Captain and the World of Tomorrow, Sin City, 300 and the Star Wars prequels their distinctive look. But Hollywood has zillions of dollars to spend. What can you do on a shoestring?
All sorts of things, to be honest.
What Can Chromakey Do For You?
For the budding Tarantino, it can provide a backdrop for your actors on the cheap (or strange new worlds, for the budding Roddenberry). Take a look at this clip, in which three actors running around the beaches of Normandy with a skeletal video crew and some green screen material are digitally composited and multiplied into the '82nd Airborne.
Or scroll through the archives of Michelle Malkin's "Vent" clips from her Hot Air.com site. You might not be simpatico with Malkin's politics, but there's much for someone new to online video to learn from her video clips. The best of them boast production values (courtesy of blogger and video technician Bryan Preston) that would allow them to cut into any network nighttime news broadcast.
But getting started with green screen isn't for the faint of heart. At a bare minimum, it requires a blend of software, camera, lighting, the green screen itself.
Also note that while so far I've been calling it green screen, blue is still frequently used as well. In fact, in the past, the main color for both chromakeying and film special effects was blue screen, but beginning in the late 1970s, there was a slow film industry flip-over to green-colored screens for chromakey.