Using Set Matte

Use Set Matte to use one operator (footage or any other operator) as the alpha channel for another.

The Set Matte effect makes it easy to use one layer to modify several layers in the composite. For example, you can use the alpha channel from a keyed image to modify several layers by applying a Set Matte effect to each layer whose transparency you want to modify.

Note: Transformations to the layer that you are using as the matte layer are disregarded. If the matte layer's dimensions differ from the front layer's, the matte layer is scaled so the two layers match.

To use the Set Matte effect:

1. Select the layer to which you want to apply a matte (the layer whose transparency you want to modify).
2. Choose Operators | Channel | Set Matte.

The Set Matte Controls panel appears.



3. Click the Layer button, and then select the operator to use as a matte from the Operator Picker dialog.
4. From the Input Channel list, select which channel in the matte layer sets the alpha channel of the other layer.

For example, select Luminance to set alpha to zero where pixels are black, and to 100 where pixels are white.

5. Use Undefined Areas to specify the color used to fill in the blank (0% opacity) areas of the image.

To do this, click the Pick button to select a color from the viewport, or click the color box to choose a color from the color picker.

6. Set the Blend value to a value below 100% to partially see through to the original layer.