Nuke gets very powerful the more you use its layer and channel system. Ask any nuke artist and many will say the same thing. It's one of those features that you wonder how you lived without for so long.

Let me explain.

In compositing you have layers and channels. Each layer can have 4 channels. R for red, G for green and B for blue. The 4th channel being the alpha channel. That comes in black or white.

In Nuke you can have more than that. You can make them on the fly as your compositing. They can also come from a outside source such as a 3d application, or even Photoshop.

Everyday i work with source plates that includes and red channel, a green channel and blue channel. The alpha is either black or white. Now things can get fancy. Say I do color correction to the source plate. I also make a clean plate so we can replace/hide an object or talent. Both the clean plate and the color corrected src plate can have its own named layer and channels to go with it.

We can also do this with mattes. We can create a new channel called door.matte. Now anywhere in the compositing tree you can use that channel to control color of anything else you might need.This gets even more cool with normals passes and other fancy images that applications can produce. This topic is for its own post.

Why is this powerful?

This makes for very clean and easily readable scripts for one. You can setup your scripts in batches or groups of nodes an not have have pipes zigzagging in the node graph. Which is nice when you are working with other artists. Rotoscoping nodes on top, tracking and other cleanup under that and so on.

Please feel free to post how you use the Layer/Channel system in nuke. and why its powerful to you in your everyday work.