The Keying > Color Keyer effect
The Color Keyer effect uses the same principle as the Luma Keyer effect. It deletes the selected color on the image or video footage of your choice.
It is no longer required to concentrate on pixel luminosity but on the entire color.
Two types of parameters may be locked with a keyframe: Tolerance and Softness.
In the FX stack above we see: the higher the value of the Tolerance parameter, the more colors close to "blue" will be deleted.
The higher the value of the Softness parameter, the less abrupt the transition between opaque and transparent pixels will be.
Opposite, most of the bluish colors of the sky and cloud become transparent.
The green and dark colors of the tree are further away from blue and therefore opaque.
With the Invert parameter, the effect can keep the color chosen in the Color parameter whereas to remove it.
The opposite image shows the result when the Invert parameter is checked.
These two keying effects may, of course, by applied to a complete footage, which makes work easier when using a scanner with loader or a recorded video sequence.
Let's take another concrete situation :
The character nearby was shot in front of a blue screen. We are going to explain how to remove this blue background and to replace it by another background.
It's a technique often used in the broadcasting world : weather reports are shot with a single-colored background which is removed and replaced by a weather chart.
Let's go back to our character : the purpose is to make transparent all the blue pixels and to display a new background on another layer. To do so, let's load a landscape background nearby and put it as an Animation layer, under the layer containing the character.
The blue color is called key color (that's why the effect is called keying).
You should have a timeline looking like this :
Now select the Color Keyer effect in the FX stack.
Choose a blue pixel from the background and adjust the tolerance and softness parameters.
Apply the effect to the whole image sequence, and here it goes, the blue background has disappeared and is replaced by the landscape.
The same method is also used to create a weather report (see below)
There are other keying effects, more complex, which have to be used in some specific situations.