Light leak
A soft warm wash of color bleeding in from one edge of the frame, like daylight sneaking into an old camera and fogging the film.
See it
What it is
On film, a bad door seal or a cracked camera body lets stray daylight hit the emulsion before it is developed, fogging it in warm orange, red, or magenta. The result washes in from one edge or corner, lifts the blacks to a hazy gray, and blows out whatever it touches. Toy cameras (Holga, Diana, Lomo LC-A) leak constantly, which is why the accident became a look.
Digitally it is one soft asymmetric gradient blob on a screen or add blend mode, anchored to a frame edge, usually paired with reduced contrast so the shadows lift instead of staying crushed. Good on photo galleries, music and film sites, wedding portfolios, anywhere you want warmth and imperfection without going full retro filter.
Gotcha: a leak that is centered or symmetric reads as a mistake, not an effect. It has to enter from an edge, fall off unevenly, and pick one warm hue rather than rainbowing. And since 'screen' only ever brightens, an already-bright image just goes milky, so grade the photo down first or mask the leak away from faces and any text sitting on top.
Ask AI for it
Add a film light leak to this image: a soft asymmetric gradient of warm orange fading into magenta, entering from the top-right corner and falling off diagonally across about a third of the frame, blurred heavily (60px+), set to 'screen' blend mode at 60 percent opacity. Lift the blacks slightly so the shadows go hazy gray instead of pure black, and keep the leak clear of the subject's face.