User Manual

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Using External Mattes
The External Matte node has evolved over the years. What was once purely a means for
importing matte channels for defining opacity and limiting adjustments has expanded to
become a way to import the RGB channels of a media file to be used for overlaying grain,
texture, and stylized distress onto an image, and even as a way to use the channels of a clip
itself as a matte.
Matte clips can be added to your project in one of two ways:
You can add mattes using the Media page, either by attaching them to a clip so a
particular matte is only available to a particular clip as part of a Clip grade, or you can
add timeline mattes that stand alone in the Media Pool, which are then available to any
Track grade.
You can also add a matte to a clip using the Media Pool in the Color page, by dragging
a clip from the Media Pool to the Node Editor. When you do so, that clip is turned into
an external matte in the current grade, which you can use as a matte for secondary
adjustments, or as a compositing layer (in conjunction with the Layer mixer) for mixing
textures or images with your grade. That clip is also automatically attached to the Media
Pool clip that corresponds to the clip you’re grading, as a clip matte, to help you keep
track of which clips are using other clips as mattes.
For more information about adding matte clips in the Media page, see “Adding and Removing
External Mattes” in Chapter 11, “Adding and Organizing Media with the Media Pool.
Whether attached or unattached, mattes operate within a grade using EXT MATTE (external
matte) nodes. EXT MATTE nodes have the following outputs:
An external matte connected to the first node of a grade
EXT MATTE Outputs: Four blue square key outputs let you output the channels
contained within the EXT MATTE node, but which channels are available affects what
is output. If the EXT MATTE node’s source clip has RGBA channels, then these are
available as Alpha, Red, Green, and Blue key outputs that you can attach to any other
node’s key input. On the other hand, if the EXT MATTE node’s source clip only has RGB
channels, then the key outputs that are made available are Y (luma), Red, Green, and
Blue, and a “Use Lum for Alpha Output” setting in the Node Editor contextual menu lets
you use the Y channel as a matte.
An interesting aspect of these four outputs is that each one is dedicated to individual A,
R, G, and B color channels. Ordinarily, External Matte clips are written with matte data
Chapter – 126 Combining Keys and Using Mattes 2859