Definition: Lens flare; Flare (on a lens);

Definition: Lens flare; Flare (on a lens); | Glossary entry

Lens flare; Flare (on a lens);

Lens flare is an image aberration caused by a variety of issues within a photographic lens. The aberration generally shows on the picture as:

  • Star-burst rings, circles or polygons: in a row or singly.
  • Haze: a washed out fog effect; washed out colours; reduced contrast; colour artefacts and rims around bright areas.
  • Haze spots or haze with lines through: in varied positions on the picture from the strongest point of light.
  • Blown out areas: not caused by Specular highlights

Here are some examples… Google images lens flare search  External link - opens new tab/page

The effect can be repeated across the scene or from one point to another. As the lens moves the effect can change its location and/or position as well as its shape and intensity.

The cause of lens flare

There are a variety of optical reasons for lens flare. The main cause is a very bright light entering the lens directly or, more often, by entering at a sharp angle from one side. Light striking the lens at a sharp angle causes it to scatter, reflect or be misdirected by lens impurities or inconsistencies in the glass. Once flare has been created it may repeat itself by internally bouncing around inside the lens or elements. The presence of more than one lens element (common in modern lenses) will tend to increase the number of flare artefacts by increasing the bounce effect.

Flare prevention

Lens flare can be considerably reduced by:

  • Not shooting into bright lights.
  • Reducing the angle of incidence and brightness of lights in the field of view of the lens.
  • Using a lens hood which will prevent light entering the lens from sharp angles to the side.
  • Using certain lens coatings which prevent surface reflectance/scatter.
  • Using high quality optical glass with less impurities and inconsistencies.
Lens flare aesthetics

Some flare effects can have an aesthetic appeal. Flare is not necessarily a bad effect in a picture. It depends on the impact on the eye. In some cases it is desirable.

Flare can be generated deliberately. The shot is taken in a way which will cause flare and in particular by leaving off the lens hood and allowing bright light to enter the lens at a sharp angle. Flare can also be added in post production by manually applying flare like characteristics, or by using a software filter to apply it.

Flare can be used to create a sense of drama, or in some cases it can introduce a realistic atmosphere. It can also be used to create a discordant or chaotic feel to an image. Some forms of flare, particularly when combined with various coloured filter effects can create a nostalgic atmosphere mimicking certain types of colour film/lens combinations from past times (1960’s in particular).

In general flare tends to create, or be associated with, very bright spots on the picture. Remember, the human eye is drawn to very bright spots. Bright flare in the picture can act as a distraction from the subject. Nevertheless, flare can be a positive addition to a picture too. Especially when used for mood enhancement or to create atmosphere.

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By Damon Guy (author and Photokonnexion editor)

Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.
See also: Editors ‘Bio’.
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