Masks, Effects, and Presets
Masks
A mask is an animated path plus mode, feather, expansion, opacity, and inversion. Modes (Add, Subtract, Intersect, Lighten, Darken) evaluate in stack order, so order changes results. Mask Path interpolates linearly by default - ease it if the motion looks mechanical. Masks shape a layer's alpha before effects render; on an adjustment layer, the mask confines where the effect applies, which is how localized blurs and grades are built.
Effects and render order
Effect Controls list effects top to bottom; rendering runs masks first, then effects in order, then transformations, then blending. Copying an effect uses standard copy/paste or Alt-drag onto another layer. Animation presets are .ffx files browsed in Effects & Presets; applying one overwrites the properties it contains, so select the specific properties first when you want a narrow application.
Matte helpers
The Set Matte effect borrows alpha or luma from another layer inside the same comp, equivalent to a track matte without the stacking constraint. Layer blending modes and alpha interpretation (straight versus premultiplied) interact - a premultiplied import with an added mask may show dark fringes.
Traps
- Animating mask feather and mask path are separate tasks; one does not follow the other.
- Mask mode order matters when three or more masks overlap.
- Effects below an adjustment layer still render; the adjustment layer only affects layers beneath it.
Worked example
To blur a face without blurring the background: add an adjustment layer above the footage, apply a blur, and draw a feathered mask on the adjustment layer. Do not put the mask on the footage layer and then add the blur - the mask would clip the footage itself rather than scope the effect.