Fixed Matte

Fixed Matte

A fixed matte sits over your image as a static black mask and remains exactly where you placed it for the entire shot. Unlike an animated matte—which moves with the action or changes the frame set—it adheres immovably to the edge of the frame or specifically frames a particular scene element. You use it to correct aspect ratios, mask unwanted image areas, or to enhance a deliberate image composition.

In practice, you work with it in editing or in After Effects: you draw your matte on a black layer, place it over the clip, and lock it for all subsequent takes. In contrast to a rotoscope mask, which you redraw frame by frame, a fixed matte saves you enormous time—especially valuable when working with long material. A classic case: you need a 2.39:1 widescreen aspect ratio in a TV spot (Cinemascope look), you place a black bar at the top and bottom, and leave it there for the entire scene. Or your cinematographer accidentally captured the boom mic shadow—apply a fixed matte over that area, and you're done.

The crucial distinction is from an animated matte: the latter follows movement or adapts to cuts. A fixed matte, on the other hand, is a visual constant—it has no keyframe setup, no motion curve. This makes it robust for exports and guarantees pixel-perfect reproducibility across all render passes. However, in the VFX workflow, you also pay a price for this rigidity: if the camera or image content shifts, the matte quickly appears unmoving and artificial. Therefore, you are most likely to use fixed mattes on truly static shots—or for intentional stylistic vignetting where artificiality is desired.

Practical tip: Always save your fixed matte layers on their own layer, uncompressed or with minimal compression. This allows the mask to be adjusted later without re-rendering the entire composite. And pay attention to the transition point: where exactly does the mask end? Soft edges (with feathering) look less harsh than hard cuts—try 2–8 pixels of feathering depending on the resolution.