Lens flare
Simulator
AI generated demo imageYour photo stays on your device. This page opens it in your browser and works on it there.
Ghosts take the shape of the aperture: round wide open, polygons when stopped down, with a starburst at small apertures.
Drag on the picture to move the light. Positions just outside the frame still flare.
Where flare comes from
A lens is a stack of glass elements, and every glass surface reflects a little of the light that hits it. A bright source sends some light bouncing back and forth between surfaces before it reaches the sensor, painting ghost images and a haze over the picture.
Ghosts
Out-of-focus images of the light, usually shaped like the aperture, strung along a line from the light through the centre of the frame. Move the light and the whole chain swings around the centre.
Veiling flare
The total of all stray reflections, spread across the frame as a haze that lifts the blacks and lowers contrast, even when no ghost is visible.
Coatings
Thin layers that cancel reflections at each surface. Uncoated glass reflects about 4–5% per surface; single coatings cut that to around 1–2%; modern multi-coatings reach a fraction of a percent, so ghosts fade from bold to faint green and magenta traces.
Starburst
At small apertures, light diffracts around the blade edges, turning bright points into stars. Each straight blade edge makes a pair of spikes.
Flags and matte boxes
If the light is outside the frame, a black flag or the matte box's eyebrow can shade the lens and remove the flare entirely. A light that's inside the frame can't be flagged off.
Flare as style
Some productions choose older, lightly coated lenses or strip coatings on purpose, because a warm, ghost-filled flare reads as sunlight, nostalgia or heat.