Pete Roythorne sets the background to special effects

If you've ever sat and wondered how they get Superman to fly over cities in the movies or manage to get real actors to appear in front of computer-generated backdrops, the answer is simple: Chroma Key technology, also known as green-screen or blue-screen technology.

Once purely the domain of high-end movie effects people, this technology is creeping into digital video use in classrooms, thanks to very affordable software such as Adobe School Collection, Ulead, Pinnacle, iMovie and KudlianSoft's I Can Animate and On-Camera, which all include Chroma Key functions as part of their packages.

So, how does it work? Put simply, Chroma Key works by rendering a specific colour transparent or invisible - most often green or blue. This means that you can film a person against an evenly lit, single-colour background and, using layer functions within your chosen video-editing package, place it over the background of your choosing. This makes it appear as though the action is taking place in a very different location: Las Vegas, a tropical rain forest or, indeed, flying with Superman - the possibilities are endless.

To make use of Chroma Key you first have to create a single-colour background. Some schools have gone to the expense of creating an entire Chroma Key wall using specialist Chroma Key paper or paint (paints cost around pound;41 for just under 4 litres), but you can also use fabric (around pound;10 per metre) to make backdrops and keep the cost down.

If you're on a really tight budget, and want to keep the cost down even further, ordinary blue or green household paint can be just as effective.

If you're having trouble thinking how this could apply to the curriculum, imagine being able to produce videos with your pupils as on-the-spot reporters at major historical events or even apply that to global current affairs.

Another option comes through Kudlian Soft's iLife Curriculum Expansion Packs which include Charting and Graphing and Weather and Geography add-ons, and these allow you to produce charts and weather maps and then superimpose pupils as weather forecasters and presenters as you'd see on the television.

In short, you can now transport your class to anywhere in the world at any time - in fact why stick to just this world?

* Creating a Chroma Key background:

* Software Adobe:

Apple's iMovie: Kudlian software:

Pinnacle Systems:


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