Do Chroma Key Video Effects
The chroma key effect has long been used to superimpose subjects over a colored background which is replaced with another image. “Chroma” refers to color, and the idea is that a background that uses a specific color will be replaced electronically with another image. The replaced image provides the illusion that the subject is in another locale or standing in front of graphical images such as weather maps or other news-related graphics. Thanks to sophisticated computer video editing software, the chroma key effect is now achievable with less expense and effort than in the days before digital video technology.
1. Choose your colored background. Either a green or blue screen has become the most popular choice for backdrops used in the key effect.
2. Construct the backdrop. The chroma key backdrop will need to be large enough to provide complete coverage for the desired scene. If using a canvas or muslin backdrop, the material should be free of any wrinkles or folds. The key backdrop should be as flat and smooth as possible.
3. Light the backdrop. For the chroma key effect to work, the backdrop must be lit as evenly as possible. Use broad lighting sources that provide consistent coverage of the backdrop.
4. Place the subject far enough in front of the backdrop to avoid shadows from the subject falling on the backdrop, or light from the backdrop reflecting onto the subject.
5. Videotape the desired scene with the camera position so the key backdrop fills the viewfinder.
6. Import the video into your video editing software.
7. Import the desired background image you wish to use to replace the colored background. Place this image below the key effect track.
8. Select the chroma key effect from the list of available filters or key effects.
9. Adjust the key controls for color range, cutoff and threshold until the colored backdrop is removed to reveal the background image. Use the effect controls to insure the edges of the foreground subject are free of any key color artifacts.