User Manual

Keep in mind that a key is just a grayscale image. Setting up this kind of node structure lets you
use any of the second node’s controls, such as the Custom Curves, Noise Reduction or Motion
Blur controls, Sharpen, Midtone Contrast, Lift/Gamma/Gain, Contrast, or Log controls, to
manipulate the key in ways you couldn’t do using only the Matte Finesse controls.
While this technique may not be necessary for conventional color isolations, it can come in very
handy when making tricky isolations with hard to key subjects, or when using one of the
Qualifier modes to pull a key to create transparency for compositing using the Node Editor’s
Alpha output. In this instance, you can connect the RGB output of a node used for key
manipulation directly to the Alpha output. In the example, Node 1 pulls a key, and the RGB is
connected to Node 3 which is used to color correct the foreground image. The key from Node 1
is connected to the RGB of Node 2, which manipulates the key to clean it up prior to connecting
it to the Alpha output block at the bottom right of the Node Editor.
Connecting a key output to an RGB input to adjust a key
used to create transparency via the Alpha output
Furthermore, this capability also lets you create keys in other ways besides using the Qualifier
palette controls. In the following example, the Contrast and Custom Curve controls in Node 3
create a high-contrast matte of the windows which is blurred. The RGB output of Node 3 is then
connected to the KEY input of Node 2, where the resulting key can be used for a variety of
adjustments; in this case, to tint the product within the image green. Alternately, this technique
could be also be used to create transparency via the Alpha output.
Using a high-contrast color correction as a key
Interconnecting key and RGB inputs and outputs is a powerful capability that lets you create
many kinds of workarounds for uncommon situations.
Chapter – 126 Combining Keys and Using Mattes 2858