What is Lens Flare

Lens flare occurs when a light source (such as the sun) is far brighter than the rest of the scene. The bright source may lie within the camera’s field‑of‑view, or sit outside the frame yet cast light onto the lens surface.

Depending on the position of the intense light source, flare may produce heavy haze and low contrast, spherical or polygonal artifacts scattered across the frame, semi‑circular shapes with rainbow‑like color fringes, or a combination of these symptoms. It originates from internal reflections inside the lens assembly, as well as reflections between the lens and image sensor.

As illustrated in the diagram: normal light rays (red) travel along the intended optical path and reach the image plane directly (green). Rays from strong light sources (blue) split and reflect off lens surfaces, eventually striking different areas of the sensor (blue dashed lines). When light is partially blocked while passing through lens elements, reflections off the aperture blades can further aggravate lens flare.

Although the diagram describes general lens‑flare behavior, manufacturers and photographers commonly distinguish two main categories: veiling flare and ghosting flare. The two often appear simultaneously. High‑quality lens coatings can substantially suppress flare artifacts.

Veiling Flare

Veiling flare typically takes place when a strong light source lies outside the camera’s field‑of‑view. The source does not show up in the image, yet its light still strikes the lens.

It generates prominent haze and reduced contrast: dark areas in the image brighten, and colors become washed‑out. Lenses with premium multi‑layer coatings help minimize veiling flare.

In the example scenario, the sun sits just above the subject and outside the captured frame, but its light still hits the lens and creates a hazy glow around the person in the shot. Veiling flare does not only affect the area near the sun; it degrades contrast across hair, facial features and clothing. In artistic shooting, this effect may be desirable to create a bright, lively atmosphere.

Nevertheless, veiling flare can be worsened by multiple factors: internal lens dust, smudged front lens element, poor‑quality or dirty optical filters, and the absence of anti‑reflection multi‑layer coatings. Under certain conditions, image quality can degrade severely.

The sample demonstrates a lens performing poorly under direct sunlight, yielding an overall foggy picture. This stems partly from missing multi‑coating technology and partly from accumulated micro‑dust inside the lens, which introduces extra internal reflections.

Ghosting Flare

Unlike veiling flare which produces foggy, low‑contrast imagery, ghosting flare refers to discrete visible artifacts within the frame. These are reflections of intense light sources or shapes mimicking the outline of the lens aperture. These colored spheres and shapes generally align along the axis of the light source and can spread across the whole frame, with dozens of possible artifact patterns. Refer to side‑by‑side comparisons of four 70‑200 mm zoom lenses.

Alongside veiling flare, circular artifacts known as ghosting flare are visible in each sample. The quantity of ghost artifacts varies according to the number of lens elements inside each optic. In general, more lens elements bring higher likelihood of ghosting. Complex‑design 70‑200 mm zoom lenses commonly show a dozen or more flare ghosts; nearly all such zoom lenses suffer from both veiling flare and ghosting flare.

This effect intensifies when stopping down to a smaller aperture. Aperture‑shaped ghosts are barely noticeable at large apertures such as f/1.4 but become very obvious at small apertures such as f/16. Polygonal ghost shapes you observe in footage are direct projections of the lens aperture blades.

Sensor / Red‑Dot Flare

Red‑dot flare (also called sensor flare) arises from light bouncing back and forth between the image sensor and the rear lens group. Distinct from ordinary lens flare caused by reflections on lens and aperture surfaces, red‑dot flare forms when light reflects off the sensor onto lens elements and bounces back onto the sensor again.

Apart from polygonal aperture‑generated ghosting flare, clusters of small red dots may appear around bright light sources such as the sun. These are magnified micro‑lens structures on the image sensor.

Factors Influencing Lens Flare

Most modern lenses adopt specialized multi‑layer anti‑reflection coatings to mitigate flare. Even top‑tier professional lenses, however, can still produce veiling flare or ghosting flare. Optimized mechanical lens design can also reduce certain flare artifacts.

1. Lens Elements: A higher count of internal lens elements increases susceptibility to flare.
2. Focal Length: Wide‑angle optics handle flare relatively well; shorter focal lengths make light sources appear smaller in‑frame. Telephoto lenses perform worse in flare resistance since they magnify everything, hence large, long lens hoods are widely used.
3. Lens Optical Design: Well‑thought‑out mechanical and optical design suppresses flare. For instance, some Nikon lenses feature recessed front elements that greatly cut flare and ghosting without relying exclusively on high‑cost coatings.

1. Multi‑Coatings: Multi‑resistant coating (MRC) on lens elements delivers major improvements in flare suppression performance.
2. Optical Filters: Low‑quality filters introduce extra flare artifacts.
3. Internal Lens Dust: Dust accumulating inside lenses over time exacerbates veiling flare.
4. Smudges and Surface Contamination: Greasy fingerprints and particles on front lens surfaces also trigger additional flare.