Blackmagic Design DaVinci Resolve Advanced Panel - Manual (Page 206)

COLOR 206
Parallel Mixer Node
When nodes are connected one after the other this Serial or Cascade configuration effectively links the
output of the first node to the input of the next and so on until the last node, which finally links to the
Node Graph output. This is the point where the Viewer and Grading monitor is connected.
As each node modifies the image it changes the range of data available to the next node. An example
would be a node one that removes all the color in the image. Its output is a black and white image and
the following node only has this black and white image to work with. You can not add color on node two
by increasing the gain for any color channel as there is no color at the input as supplied by node one.
The External Key Invert checkbox, found within the Key tab