Keying - Nuke 101: Professional Compositing and Visual Effects - page 308

image—removing the foreground element and essentially producing what's called a clean
plate. ( Plate is another word for image, and clean plate means an image without the fore-
ground object.) By this I mean, it gets rid of the foreground elements and produces only
the screen colors, green or blue. The IBKGizmo takes this clean plate, by connecting the
IBKColour's output to the IBKGizmo's c input, and uses that to create a key, including
fine detail adjustments and, if you connect a background image as well, some smart spill
suppression. The great thing about this method is that for each pixel in the screen ele-
mentyouwillhaveacorrespondingcleanplatepixel.Soitdoesn'tmatterhowuneventhe
screen is, as you are giving a different color for every part of the image using the clean
plate.
Incidentally, if you have a clean plate that was shot—as in, you asked the actors to clear
out of the frame and took a picture—you can connect the IBKGizmo's c input to that in-
stead of the IBKColour's output. This is even better as it really gives you the best source
to work with.
Thescreenelement youhaveisprettyflat,butstill, theIBKcangiveagreatresulthereas
well, especially on fine hair detail.
1. Select Read2 and hold Shift to branch an IBKColour node from the Keyer tool-
box.
2. Select Read2 again and branch an IBKGizmo node from the Keyer toolbox.
3. Connect IBKGizmoV3_1's c input to the output of IBKColourV3_1.
4. Connect IBKGizmoV3_1's bg input to the output of Read1.
You are connecting the background image to the Keyer so that the spill suppres-
sion will factor in the background colors.
Your tree should now look like FIGURE 7.12 .
Figure 7.12. Setting up an IBK tree.