Light leak; light wrap
Light leak is a film-like wash; light wrap borrows background light along a cutout's edge so a composite feels photographed together.
See it
What it is
These names describe different kinds of spill. A light leak is stray light reaching film or a sensor, often appearing as a soft red, orange, or white wash from the frame edge, the same artifact you get on the first frames of a 35mm stills roll or from a leaky plastic Holga. Light wrap is a compositing technique: a blurred copy of the background is allowed to creep a few pixels inside the foreground matte, imitating bright background light wrapping around the subject.
Reach for light wrap to seat a keyed subject into a bright sky, window, or stage plate. Reach for a light leak as an analog texture or transition when the footage can plausibly tolerate an exposed-film artifact. The source color and direction should come from the shot.
Gotcha: a stock light-leak overlay does not fix a composite. Good light wrap is narrow, soft, and limited to edges facing a bright background. A thick uniform halo shrinks the subject, contaminates hair and skin, and advertises the matte instead of hiding it.
Ask AI for it
Create light wrap in Adobe After Effects, not a stock light-leak overlay. Duplicate the background above the keyed subject, apply Gaussian Blur at 30 to 50 pixels, use Set Matte with the subject alpha, then duplicate that layer, apply Simple Choker at 4 to 8 pixels to the copy, and set the copy's blend mode to Silhouette Alpha so only a narrow inner edge remains. Composite the result with Screen at 20 to 30 percent, limit it to edges facing bright background areas, and keep the subject's core and shadow-side edge clean.