Keying - Nuke 101: Professional Compositing and Visual Effects - page 317

2. Make sure you are viewing the output of Keylight1, and viewing the RGB chan-
nels.
Keylight has four inputs ( FIGURE 7.25 ):
• Source: The first and main input—often the only input you will use. This
is where the element to key should go in. This input should already be
connected to your greenscreen element.
• Bg: Youcanconnectabackgroundimagehere.BecauseKeylightalsosup-
presses spill, it can use the color of the background for that suppression
(and it does so by default if the input is filled). Keylight can also actually
composite over the background, although this is rarely done.
• InM: Stands for inside matte (also called holdout matte ). If you have a
black-and-white image (roto or other rough key), you can use it with this
input to tell Keylight not to key out this area. This can also be called a
core matte .
• OutM: Stands for output matte (also called garbage matte ). If you have a
black-and-white image (again through a roto or a rough key), you can use
it with this input to tell Keylight to make all this area black.
Figure 7.25. Keylight's four inputs (marked with dots so you can see them).