How to Working With Green or Blue Screens in Home?

Being able to fly, walk on an alien world or survive a spectacular accident is par for the course in most blockbuster Hollywood movies. But obviously none of it is real – it's all done with smoke and mirrors, or more precisely, chroma keying.

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. Green or blue are used because both colours are the furthest away from all human skin tones.

One of iMovie's advanced tools is the ability to automatically remove a green or blue background from a clip. But how do you get such a background in the first place?

Low budget

That's where it gets a little complicated, but it's perfectly achievable and the results are very effective, even on a low budget. Then you'll be able to be anywhere in the world. You'll need to get yourself some equipment, none of which is optional if you want the effect to work properly.

The first one is a backdrop. 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. Otherwise, eBay has a lot of resellers offering affordable chroma key backdrops.

What's more important is the lighting. You need to evenly light your backdrop; then you'll need to light your subject separately. 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.

Since you're on a budget, you need to find workarounds to expensive modern professional lights. Twin 500W halogen work lights on a tripod will do an excellent job. Get two sets – one for either side of the screen.

Using the same lighting system for your subject would completely wash it out. Getting redheads is probably your best bet as it's not the most recent technology, so you can get them cheaper. Again: eBay. Make sure you get at least two to light your subject evenly.

Lastly, you need to make sure your camera will remain static for the whole duration of the shoot, so either place it on a shelf or stool, or invest in a tripod. Since the purpose is to keep the camera motionless, the most basic tripod will do. You won't be able to do tracking shots or follow the subject as they walk around; you'd have to match the movement with the background exactly and this can only be done with motion-tracking cameras.

Light placing

Next, you'll have to experiment to make sure the lighting is in the right place for the effect to work, and then import the footage into iMovie.


Then you need to make sure the program's Advanced Tools are turned on (done from the Preferences window). Then, add your backdrop onto your project and drag your green/blue screen clip on top of it.

Select the appropriate pop-up option and the background clip should appear behind your subject.