Darken the corners of a clip so the eye settles on the middle of the frame. The vignette is a smooth radial gradient that follows the frame’s aspect ratio.
Strength, size, and feather
Strength sets how dark the edges get. Size sets how much of the center stays untouched, and Feather how soft the transition is. A strength around 40% with a high feather is barely noticed but still steers attention; 80% and above reads as a deliberate stylistic frame.
Consistent across cuts
The vignette is the same on every frame and does not react to the picture, so it holds steady across cuts and camera moves. For the steep, uneven falloff of a lensless camera, use the pinhole video effect.