How to Create an “Outside” Node from Multiple Power Windows in Different Nodes – Key Mixer Node

This shot had multiple windows that needed to be isolated for color grading. Ideally, each window would be in a separate node so you can grade them individually. The challenge was finding a way to grade everything else outside both windows. For one window, you can add an “Outside Node.” Or, the cleaner solution is to add a parallel node, copy the node with the Power Window and paste it onto the new node, then invert the Power Window. Both methods didn’t address the problem:

  • You can’t copy and paste just a power window into a node that already has a power window – it just replaces it, instead of adding it, which would have given us the option of copying to a new node and inverting it

I was stuck with two nodes that had rotoscoped windows in a dolly shot! So though it seems the easy solution would’ve been to create a new node with two power windows in it, it wouldn’t have made sense to get rid of all the work I had just done rotoscoping.

In comes the Key Mixer Node! I finally found a solution on some random forum where someone was in the same situation as me. It essentially creates an alpha matte based on any number of Power Windows that feeds into it. You have to create it by right-clicking a blank space on the Node graph, then feed the appropriate nodes as shown in the display (using the blue triangles).

This will both allow you to make an outside node from any number of power windows, as well as live within a parallel node so that it’s a clean border between the power windows and the rest of the image.

I hope you found this useful! Please comment below if you have any questions or other tips you’d like to share with us.

Nelson Nunez
Nelson Nunez
Nelson has been producing and editing since the days of VHS tape (remember those things?). It has grown from a hobby, to a passion, to a profession. His love for puzzle-solving and storytelling take hold when he gets to craft a new story, frame by frame. Nelson holds a B.S. in Television, Film, and New Media. When he’s not making magic happen on set or in the edit cave, he likes to teach his son to breakdance, hold his newborn daughter in his arms, and take his wife on spontaneous food adventures!
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