Definition
When you shine a flashlight onto a windowpane, light bounces off the glass instead of passing straight through, casting glowing patches. Lens flare is an optical phenomenon where bright light, like the sun or a spotlight, enters a camera lens and scatters across the glass elements and internal parts, showing up as glowing circles, streaks, or a misty haze in photos and videos.
Why Do Glowing Circles and Misty Hazes Appear in Cameras?
Have you ever snapped a photo on a sunny day and noticed rainbow circles or small polygons strung out across the frame? Sometimes the entire photo looks washed out, covered in a milky haze. This happens because a camera lens is not just a single piece of glass.
To capture crisp images, modern camera lenses stack multiple glass elements together, combining convex and concave shapes. Most incoming light travels straight through to the digital sensor, but intense light bounces off the glass surfaces and scatters inside the barrel. These stray light rays bounce between the elements and strike the sensor, creating unwanted visual artifacts from internal reflections.
When light scatters widely and washes out the entire shot with a misty fog, photographers call it 'veiling flare.' When stray light forms distinct geometric shapes mirroring the lens or aperture blades, it is called 'ghosting.' Both are born from uncontrolled beams of intense light bouncing inside the lens.
A Closer Look at the Physics
To be more precise, lens flare is driven by optical physics—specifically refractive index differences, light wavelengths, and the camera's internal hardware. With plain, uncoated glass, about 4% of light reflects at every boundary between air and glass. A high-end lens with ten separate elements has up to twenty glass-air surfaces. Without treatment, stray light would ricochet everywhere inside the barrel.
As this reflected light passes through the camera's aperture—the opening controlled by overlapping mechanical blades—it gets clipped into polygonal shapes like hexagons or octagons. In addition, different colors of visible light (red, green, blue) bend at slightly different angles, often fringing flares with vibrant rainbow borders.
To fight this, optical manufacturers apply nanometer-thin layers of special anti-reflective coatings to the glass. These coatings use destructive light interference to cancel out reflections. High-end lenses feature advanced multicoatings that suppress flare and ghosting almost entirely.
Why Tech and Art Add It on Purpose
In optical engineering, flare was originally a flaw to eliminate because it degrades contrast and sharpness. Yet filmmakers and game developers embraced it as visual magic to heighten realism and mood. It reminds the audience that they are witnessing a real, physical scene through a camera lens.
In 3D graphics and video games, digital artists use specialized shader programs to simulate lens flare mathematically. The software tracks virtual light sources and paints procedural ghost rings, streaks, and glows whenever the sun or a spotlight hits the camera view. Sci-fi and action movies frequently shoot with anamorphic lenses for signature horizontal flares, or overlay computer-generated artificial lens flare in post-production.
Meanwhile, modern smartphone cameras use AI algorithms to detect and erase glare from night streetlights. What began as an optical defect is now treated both as a cinematic art style and as a challenge for smart software.
Common misconceptions
Lens flare means the camera lens or sensor is defective.
It is a natural optical phenomenon caused by light passing through multiple glass elements, not a defect. Even the most expensive professional lenses will produce flare when pointed straight into a bright light source.
Where you meet it
Golden-hour portrait photos where bright backlight scatters warm, circular glowing spots across the frame.
Sci-fi spaceship movies where stars and sunbeams produce cinematic blue horizontal streaks across the screen.
In one sentence
Lens flare is a halo or streak of light caused by reflections inside a camera lens, widely used today as a dramatic visual effect.