What’s one thing that makes television more interesting? That’s right, effects! Built into every production switch board is the special-effects generator (SEG) able to create a variety of special effects. Because of advances in the production and effects world, certain effects have lost their specialty status and are now considered to be part of the standard visual arsenal. These effects are superimposition, the key, the chroma key, and the wipe.
Superimposition is a form of double exposure where one image is electronically inserted over another. It is important to note that in superimposed images, the image being transposed upon can still be seen through the new image. It is used primarily to create inner effects- thoughts, dreams, or imagination processes.
Keying is the process of electronically cutting out a portion of an image and filling them in with another. Keying is used primarily to add titles to background images or to position another picture into the background. Unlike superimposition, keying does not mean that you can still see the original image behind the key.
Chroma keying uses a specific color, usually blue or green as a background for the object that is to appear in front of the background. Sound familiar? Think green screen. This tool uses color to define regions and replaces those regions with images. An example? Think about the weather person telling us about the rain coming. The image he is interacting with is not physically behind him/her, but it is being electronically inserted via chroma key.
A wipe involves a second image coming into frame and eventually replacing some, most, or all of the original image. Wipes can be vertical, (coming from the top or bottom of the screen), horizontal (coming from the left or right of the screen), or in some other preprogrammed shape such as a diamond coming from the center. Wipes can also be set to be soft, so the edges of the wipe are feathered and not as harsh. Wipes can be used to split screens so that the audience has two different views on screen. An example of this is when news networks do interviews with people in various locations. One person in the studio will be seen on one side, and the guest will occupy the other half of the screen space.