Make sure you get at least two to light your subject evenly. Getting redheads is probably your best bet as it's not the most recent technology, so you can get them cheaper. Using the same lighting system for your subject would completely wash it out. Get two sets – one for either side of the screen. Twin 500W halogen work lights on a tripod will do an excellent job. Since you're on a budget, you need to find workarounds to expensive modern professional lights. This way, it'll be much easier to find the edges around the subject to avoid a potential halo around it when the backdrop is cut.

You need to evenly light your backdrop then you'll need to light your subject separately. Otherwise, eBay has a lot of resellers offering affordable chroma key backdrops.

If you already have a green or blue sheet, or even a wall of the appropriate colour, you could experiment with it and see if it works as expected. You'll need to get yourself some equipment, none of which is optional if you want the effect to work properly. Then you'll be able to be anywhere in the world. That's where it gets a little complicated, but it's perfectly achievable and the results are very effective, even on a low budget. But how do you get such a background in the first place? Low budget One of iMovie's advanced tools is the ability to automatically remove a green or blue background from a clip. Green or blue are used because both colours are the furthest away from all human skin tones. The idea behind the process is that it's easy to cut out a single colour, rendering it transparent and allowing you to put something else in its place. But obviously none of it is real – it's all done with smoke and mirrors, or more precisely, chroma keying. Being able to fly, walk on an alien world or survive a spectacular accident is par for the course in most blockbuster Hollywood movies.

How to do green screen effect on imovie