Chroma key uses a green or blue background while filming.
Chroma key is a popular method of fusing computer animation with live video. Backdrops or various items on the set will use a specific shade of blue or green, depending on the version of chroma key software you are using. Computers can then be used to apply a photo, scene or animation to anything on the video of the designated shade of blue or green. This results in the chroma key method often being referred to as either "blue screen" or "green screen." Chroma key can be used in a variety of ways to enhance your video production.
Chroma Key Backdrops
Using chroma key for backdrops is the most widely used technique for green screen technology. A green or blue backdrop is hung in place, with screen actors positioned directly in front. This allows you to have animated backgrounds that bring presentation videos to life, or to create a complete set with computers. Using backdrops in this manner allows you to make it look like your actors are in virtually any location imaginable.
The key to successfully using chroma key backdrops is the lighting. Use box lighting to illuminate your actors, but remember that the backdrop also needs lighting. If the only light source is the one that is intended for actors, it will cast shadows onto the backdrop. These shadows will degrade the quality of your backdrop video. To prevent this from happening, use a second set of lights, positioned behind the actors but still out of sight of the camera, intended to illuminate the backdrop alone. With the backdrop having it's own light source, any shadows will be overpowered and you will have a clean video production.
Chroma Key Props
Sometimes chroma key is used in small amounts. This is a tactical approach that confines the computerized part of the film to a highly targeted area. Sometimes news rooms use this technology to pin a small piece of green or blue material behind the news anchor, allowing them to rotate computerized images from behind the scenes. Small pieces of the green or blue material can also be applied to the front of the news desk, allowing the computer the display advertisements or to scroll stock values. Those who are making traditional films can use this technique to make ordinary props have a totally different appearance, simply by wrapping them in green material and then using a computer to replace the prop with a computer generated image.
Chroma Key Characters
Some films call for exotics characters that can not easily be created with traditional makeup and costumes. Chroma key is the perfect solution to this problem. Actors can wear a chroma key body suit, which covers them in either green or blue material. The computer can then use chroma key software to replace the actor with the character of choice. This use of chroma key is a way of seamlessly integrating computer animations with live action.
Tags: green blue, blue material, green blue material, blue green, chroma software, green screen
