Working with External Mattes in DaVinci Resolve, Part 1

In Action – Working with Alpha Channels Part 1

May 22, 2017

Working with key signals in DaVinci Resolve isn't hard - but it's not intuitive either. Once you figure it out, it's also a power feature. Learn more.


How to Manage Key Signals and Alpha Outputs in DaVinci Resolve

Working with key signals in DaVinci Resolve doesn’t have to be complicated – but it’s not intuitive either. And once you get the basics down, you start to realize how Resolve’s handling of key signals allows for some sophisticated secondary corrections.

If you’re new to working with external mattes then you’ll want some quick definitions of the terms I’m using in this 2-part Insight:

  • External Matte – These are video clips of rotoscoped elements generated (usually) from another software package, such as After Effects or Mocha Pro. They are usually rendered as pure grayscale video images (although there are other workflows).
"Convert to Matte Clip" Command in DaVinci Resolve 14's Media Page
To convert a clip in the Media Pool into a ‘Matte Clip’, in DaVinci Resolve 14 right-click on the clip and select ‘Add as Matte for Color Page Clip’
A folder of external mattes for a car commercial
This is a folder of external mattes for a car commercial. These clips can be added as a node in the Color Page.
  • Key Signal / Matte Channel – The Key Output of a node is what I interchangeably call a Key Signal or the Matte Channel. In DaVinci Resolve, to quickly see the Key Output of a node, just put yourself into Highlight mode. What you see in the Black & White Highlight mode is precisely the Key Output of a node.
An external matte feeding multiple Key Inputs.
This is an example of a single external matte feeding the Key Input of multiple nodes.
  • Alpha Output – In DaVinci Resolve, the Alpha Output usually refers to the output of the Node Editor. If you have multiple video tracks, you add an Alpha Output to see¬†lower¬†video tracks below it.
An Alpha Output has been added on this Node Graph
The Key Ouput of Node 1 is feeding the Alpha Output of the Node Editor (the blue box below the green box on the far right-hand side of the Node Editor). This sky isolation will be keyed on top of any video tracks below it.

Part 1: Exploring Multiple Uses of Key Signals in DaVinci Resolve

In this Insight I’m breaking down one shot in a car commercial, specifically looking at how I managed these different types of key signals. My goal is for you to start thinking about the different ways of using key signals beyond just ‘punching a hole’.

In Part 2 we explore how to combine key signals to build custom matte channels directly within the Node Editor.

Got questions or comments?

As always, use the comments to share your thoughts and start a conversation.


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