Mattes can be still or motion layers . Create your own mattes in Photoshop. Go to File>New>and choose a resolution of the layer you want to affect.
In both alpha channel mattes and luminance mattes, darker (black) pixels will be transparent and lighter (white) pixels will be opaque . Intermediate shades will produce partial transparency. For soft edges on a matte, use a diffuse brush, run the Gaussian Blur filter, or feather your edges.