Why is it called Green Screen? The idea is that, by using a bright yellow-green color of paint to serve as the backdrop to your film, those colors can then be eliminated in post production. This leaves your background completely transparent, allowing you to add a second frame which creates new scenery behind your action.
To begin, you need to create a suitable Green Screen environment. The backdrop used should be a completely flat surface. Although there is specialty paint that you can buy which is designed to reflect as little light as possible, visit your local hardware store and select a flat, matte color that is as bright a green as possible. There has been some debate over whether it is better to use a blue or green color for your background. Some say that is your characters are blonde, it is better to use a blue color. If your characters are brunette, your background should then be green. There really is not much of a difference, but remember that any blue or green colors in the foreground of your set will become transparent in post-production. This can produce an eerie effect if you have not taken this into account before determining the color of your character’s eyes.
When you have painted a solid, flat surface, arrange your props and characters at least six feet away from your vertical backdrop. The trick is to ensure that you are able to properly light your set without casting any shadows onto the Green Screen. If there is a lighting discrepancy, you will find it next to impossible to create a truly transparent background.
Be very careful when lighting your set. Not only do you need to make sure not to cast any shadows on the Green Screen, but projecting too harsh a light on your set will illuminate the backdrop with hot spots as well as reflect green light onto the objects in the foreground. The green screen should never have lighting play with the original color tint.
Some animators choose to light their sets from the side or the top, immediately off camera. You can even place a light behind your set and illuminate them with a sort of “halo” effect in order to set them apart from the Green Screen.
When you have finished shooting your sequence and captured the footage into an animation software program, use the chroma key feature to erase the Green Screen. Now, you can use a separate frame to replace the background, and there you have it! Your tiny wooden ship can be surrounded by swirling, ominous waves. Clouds can race over your set with time-lapse speed. Your characters can find themselves in a swirling whirlpool, nearing an open bathtub drain. Shooting in Green Screen will allow you to create otherwise impossible effects for your animated world, with little out-of-pocket expense.