About Mask Objects

You create mask objects in the Paint operator or in any of the three mask operators.

The three mask operators are the same, but their behavior when they are applied differs.

Operator:	Behavior:
Draw Mask	The Polygon Mask tool is selected so you can immediately begin adding control points. Mask objects are not created automatically.
Elliptical Mask	An elliptical mask is created automatically.
Rectangular Mask	A rectangular mask is created automatically.

A mask operator has three features that the Paint operator does not: Global Apply Mode, Alpha Color, and Background Source.

If you only need to create a mask (or need to use these three features), use a mask operator. Use a Paint operator if you want to use Paint features in addition to the mask tools (for example, if you want to isolate a region of the image and then retouch it).

In either case, you create mask objects, which behave the same way as Paint objects. For example, you can select an object after it is created and change any of its properties. If you draw an object on top of another object, you can still select the previous object, change it, even move it on top of the newer one. For more information, see About Objects.

You can create many mask objects in one operator, so you do not need to add a new operator for each one. The mask objects can be combined in several ways (such as adding, subtracting, and intersecting).

Each mask object has transform properties to change position, rotation, scaling, shearing, and the pivot point. In addition to combining and inverting mask objects, you can feather the edges.

For subjects with inherent motion blur, or poor blue- or green-screen clips, you have precise control over the inner and outer edge softness of a mask, including variable softness for each control point on the mask spline. This feature is called the Edge Gradient.

In addition to the opacity of a mask object, the mask operators have Alpha Color (the ability to give precedence to mask objects higher in the stack) and Global Apply Mode (the ability to combine all the mask objects in an operator with the alpha channel of the input source).

The mask operators also have Background Source, a visual aid that shows a background image or clip as you are masking.