Green Screen/ Chroma Key Research

Since I can not afford to have different colour backgrounds i need to use green screen since its less costly.

It is used in Hollywood blockbusters and on TV shows to create sets and backgrounds that would be too costly or even impossible to build.

How to use Chroma Key:

The first thing you need to have is a green background, and there are several ways to achieve this.The next thing you will need is the one thing most people tend to forget and try to do without. And it always results in very poor results.

Lighting. You will need at least three light sources, preferably softboxes or 'umbrella' reflector lights. Two of the lights will be on the green screen (One either side at 45 degrees facing the back-drop), and one will be on your subject or presenter directly behind the camcorder (Ideally two lights for this as well, but you can get away with just using the one).

The presenter needs to be at least three feet from the back-drop, so they do not cast any shadow onto the chroma key background (Shadows and creases in the back-drop will make it harder to get a good chroma key effect when we start using the video editing software later on).

So the trick to great chroma key is to fill the back-drop with soft even light that is twice as bright as the light on the foreground object or presenter and avoid any shadows (or creases) on the back-drop.

Remember NOT to wear anything that is similar in colour to the green back-drop.

If you do, when you add the chroma key effect in your video editing software later, the background video or image you add will be seen on that item of clothing as well.

This can be used to good effect, if you want something to disappear for instance, just cover it with another piece of green cloth, and the background image will appear on it making it seem like it has just disappeared.

But there is the danger of using chromakey just because it seems cool to do, and the results can often look very poor and gimmicky. Chroma key is very hard to do really well, and I recommend just using plain coloured back drops (black, white etc.) or a simple background set (Like a desk, computer and plant for example) for most videos, as they look much more professional and don't require as much technical input as chroma key.

You only require two lights for a set or plain back-drops, and the video editing doesn't require any special techniques or software.

Rource for this research: http://www.webvideofordummies.com/greenscreentutorial.html