Logic Op Node
 
 
 

The Logic Op node accepts a front, back, and matte clip.

Logical Operations box
Select the logical operation you want to use to combine the source images.
Swap Inputs button
Enable to switch the ordering of the Front and Back inputs.
Transparency field
Displays the percentage of the back clip that is used in the operation.
Clamp Render box
Select a clamping option for colour and luminance values on output in the 16-bit floating point processing pipeline.

The Logic Op node processes missing media in clips set to No Media based on the input tab it is connected to.

Input Result
Front No media
Back Black frames
Matte White frames

See Using Logical Operations.