Tektronix 2200 Manual Do Utilizador

3-9

A key is an effect in which parts of one picture are inserted into 
another to create a composite picture. For example, keys are used 
to insert captions, to place a small news scene or graphic over the 
shoulder of a newscaster, or to place the image of a weather 
reporter in front of a weather map. There are several types of keys, 
each of which serves a different purpose. These will be briefly 
described on the following pages.

A luminance key, shown in 

, uses the brightness 

information in one picture, called the key source to cut a hole in 
another picture, called the background. A third picture, called the 
fill, is inserted into the hole to fill it. A clip control allows the 
operator to set the level of key source brightness that will cut the 
hole so that any part of the picture that is lower in brightness than 
the clip setting is ignored and will not cut the hole. The operator 
can also invert the key so that dark areas of the source cut the hole 
instead of bright areas.

Key Source

Fill Video