Lens Flares
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A lens flare happens when light is scattered, or ''flared'', in a
lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...
system, often in response to a bright light, producing a sometimes undesirable artifact in the image. This happens through light scattered by the imaging mechanism itself, for example through internal reflection and
forward scatter Forward scattering is the deflection of waves by small angles so that they continue to move in close to the same direction as before the scattering. It can occur with all types of waves, for instance light, ultraviolet radiation, X-rays as well as ...
from material imperfections in the lens. Lenses with large numbers of elements such as zooms tend to have more lens flare, as they contain a relatively large number of interfaces at which internal scattering may occur. These mechanisms differ from the focused image generation mechanism, which depends on rays from the refraction of light from the subject itself. There are two types of flare: visible artifacts and
glare Glare may refer to: * Glare (vision), difficulty seeing in the presence of very bright light * Glaring, a facial expression of squinted eyes and look of contempt * A call collision in telecommunications * GLARE, Glass reinforced aluminium, an ...
across the image. The glare makes the image look "washed out" by reducing contrast and
color saturation Colorfulness, chroma and saturation are attributes of perceived color relating to chromatic intensity. As defined formally by the International Commission on Illumination (CIE) they respectively describe three different aspects of chromatic ...
(adding light to dark image regions, and adding white to saturated regions, reducing their saturation). Visible artifacts, usually in the shape of the
aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...
made by the
iris diaphragm In optics, a diaphragm is a thin opaque structure with an opening (aperture) at its center. The role of the diaphragm is to ''stop'' the passage of light, except for the light passing through the ''aperture''. Thus it is also called a stop (an a ...
, are formed when light follows a pathway through the lens that contains one or more reflections from the lens surfaces. Flare is particularly caused by very bright light sources. Most commonly, this occurs when aiming toward the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
(when the Sun is in frame or the lens is pointed sunward), and is reduced by using a
lens hood In photography, a lens hood or lens shade is a device used on the front end of a photographic lens, lens to block the Sun or other light source(s) to prevent glare (vision), glare and lens flare. Lens hoods may also be used to protect the lens fr ...
or other shade. For good-quality optical systems, and for most images (which do not have a bright light shining into the lens), flare is a secondary effect that is widely distributed across the image and thus not visible, although it does reduce contrast.


Manifestation

The spatial distribution of the lens flare typically manifests as several starbursts, rings, or circles in a row across the image or view. Lens flare patterns typically spread widely across the scene and change location with the camera's movement relative to light sources, tracking with the light position and fading as the camera points away from the bright light until it causes no flare at all. The specific spatial distribution of the flare depends on the shape of the
aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...
of the image formation elements. For example, if the lens has a 6-bladed aperture, the flare may have a hexagonal pattern. Such internal scattering is also present in the human eye, and manifests in an unwanted veiling
glare Glare may refer to: * Glare (vision), difficulty seeing in the presence of very bright light * Glaring, a facial expression of squinted eyes and look of contempt * A call collision in telecommunications * GLARE, Glass reinforced aluminium, an ...
most obvious when viewing very bright lights or highly reflective surfaces. In some situations,
eyelash An eyelash (also called lash) (Neo-Latin: ''cilium'', plural ''cilia'') is one of the hairs that grows at the edges of the top and bottom eyelids, spanning outwards and away from the eyes. The lashes grow in up to six layers on each of the upper ...
es can also create flare-like irregularities, although these are technically diffraction artifacts. When a bright light source is shining on the lens but not in its field of view, lens flare appears as a haze that washes out the image and reduces contrast. This can be avoided by shading the lens using a
lens hood In photography, a lens hood or lens shade is a device used on the front end of a photographic lens, lens to block the Sun or other light source(s) to prevent glare (vision), glare and lens flare. Lens hoods may also be used to protect the lens fr ...
. In a studio, a gobo or set of barn doors can be attached to the lighting to keep it from shining on the camera. Filters can be attached to the camera lens which will also minimise lens flare, which is especially useful for outdoor photographers. When using an
anamorphic lens Anamorphic format is a cinematography technique that captures widescreen images using recording media with narrower native aspect ratios. Originally developed for 35 mm film to create widescreen presentations without sacrificing image ar ...
, as is common in analog cinematography, lens flare can manifest itself as horizontal lines. This is most commonly seen in car headlights in a dark scene, and may be desired as part of the "film look".


Deliberate use

A lens flare is often deliberately used to invoke a sense of drama. A lens flare is also useful when added to an artificial or modified image composition because it adds a sense of realism, implying that the image is an un-edited original photograph of a "real life" scene. For both of these reasons (implying realism and/or drama) artificial lens flare is a common effect in various graphics editing programs, although its use can be a point of contention among professional
graphic design Graphic design is a profession, academic discipline and applied art that involves creating visual communications intended to transmit specific messages to social groups, with specific objectives. Graphic design is an interdisciplinary branch of ...
ers. Lens flare was one of the first special effects developed for
computer graphics Computer graphics deals with generating images and art with the aid of computers. Computer graphics is a core technology in digital photography, film, video games, digital art, cell phone and computer displays, and many specialized applications. ...
because it can be imitated using relatively simple means. Basic flare-like effects, for instance in
video games A video game or computer game is an electronic game that involves interaction with a user interface or input device (such as a joystick, game controller, controller, computer keyboard, keyboard, or motion sensing device) to generate visual fe ...
, can be obtained by drawing starburst, ring, and disc textures over the image and moving them as the location of the light source changes. More sophisticated rendering techniques have been developed based on ray tracing or
photon mapping In computer graphics, photon mapping is a two-pass global illumination rendering algorithm developed by Henrik Wann Jensen between 1995 and 2001Jensen, H. (1996). ''Global Illumination using Photon Maps''. nlineAvailable at: http://graphics.sta ...
. Lens flare was typically avoided by
Hollywood Hollywood usually refers to: * Hollywood, Los Angeles, a neighborhood in California * Hollywood, a metonym for the cinema of the United States Hollywood may also refer to: Places United States * Hollywood District (disambiguation) * Hollywood ...
cinematographers, but the director J. J. Abrams deliberately added numerous lens flares to his films ''
Star Trek ''Star Trek'' is an American science fiction media franchise created by Gene Roddenberry, which began with the Star Trek: The Original Series, series of the same name and became a worldwide Popular culture, pop-culture Cultural influence of ...
'' (2009) and '' Super 8'' (2011) by aiming powerful off-camera light sources at the lens. He explained in an interview about ''Star Trek'': "I wanted a visual system that felt unique. I know there are certain shots where even I watch and think, 'Oh that's ridiculous, that was too many.' But I love the idea that the future was so bright it couldn't be contained in the frame." Many complained of the frequent use; Abrams conceded it was "overdone, in some places." In contrast, the low-budget independent film ''
Easy Rider ''Easy Rider'' is a 1969 American road drama film written by Peter Fonda, Dennis Hopper, and Terry Southern. It was produced by Fonda and directed by Hopper. Fonda and Hopper play two bikers who travel through the American Southwest and the S ...
'' (1969) contains numerous incidental lens flares that resulted from Harrison Arnold's need to modify a camera car for his
Arriflex Arri Group () (stylized as "ARRI") is a German manufacturer of motion picture film equipment. Based in Munich, the company was founded in 1917. It produces professional motion picture cameras, lenses, lighting and post-production equipment. It ...
as he shot motorcycle footage against landscapes of the
Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...
. David Boyd, the director of photography of the sci-fi series ''
Firefly The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...
'', desired this style's evocation of 1970s television so much that he sent back cutting-edge lenses that reduced lens flare in exchange for cheaper ones.Whedon, ''Firefly: The Complete Series: "Serenity" Commentary''


Other forms of photographic flare


Filter flare

The use of
photographic filter In photography and cinematography, a filter is a camera accessory consisting of an optical filter that can be inserted into the optical path. The filter can be of a square or oblong shape and mounted in a holder accessory, or, more commonly, a ...
s can cause flare, particularly ghosts of bright lights (under
central inversion In geometry, a point reflection (also called a point inversion or central inversion) is a geometric transformation of affine space in which every point (geometry), point is reflected across a designated inversion center, which remains Fixed p ...
). This can be eliminated by not using a filter, and reduced by using higher-quality filters or narrower aperture.


Diffraction artifact in digital cameras

One form of flare is specific to
digital cameras A digital camera, also called a digicam, is a camera that captures photographs in digital memory. Most cameras produced today are digital, largely replacing those that capture images on photographic film or film stock. Digital cameras are now ...
. With the sun shining on an unprotected lens, a group of small rainbows appears. This artifact is formed by internal diffraction on the
image sensor An image sensor or imager is a sensor that detects and conveys information used to form an image. It does so by converting the variable attenuation of light waves (as they refraction, pass through or reflection (physics), reflect off objects) into s ...
, which acts like a
diffraction grating In optics, a diffraction grating is an optical grating with a periodic structure that diffraction, diffracts light, or another type of electromagnetic radiation, into several beams traveling in different directions (i.e., different diffractio ...
. Unlike true lens flare, this artifact is not visible in the eyepiece of a digital
SLR camera In photography, a single-lens reflex camera (SLR) is a type of camera that uses a mirror and prism system to allow photographers to view through the lens and see exactly what will be captured. SLRs became the dominant design for professional a ...
, making it more difficult to avoid.


Gallery

File:Lens Flare.jpg, Photograph of an
Apollo Lunar Module The Apollo Lunar Module (LM ), originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed sp ...
containing lens flare. Besides the obvious flare around the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, the light artifacts at the bottom right are also caused by flare. File:Artificial lens flare.png, Sample of artificial lens flare, as might be used in an animated movie or video game File:High-quality lens flare rendering.png, High-end lens flare rendering using a recent technique File:Edinburgh-Princesstreet2.jpg, Lens flare is extremely difficult to control when a bright light source like the Sun is just outside the frame. File:Firework with lens flare.jpg, When the subject of a photo is the light source itself, lens flare can be a desirable and dramatic effect. File:Solar eclipse Austria 2011 Jan 04.JPG, Lens flare used to capture details of too bright motive (partial
solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...
) File:20100525 Imbros Marmaros Turkey example of Lens Flare.jpg, Lens flare—the Sun is outside the frame. File:Mograph lensflare.png, Lens flare commonly associated with the use of anamorphic lenses which are often used in the production of films File:Kensington Palace Gardens - London - UK.jpg, Lens flare example in picture of
Kensington Gardens Kensington Gardens, once the private gardens of Kensington Palace, are among the Royal Parks of London. The gardens are shared by the City of Westminster and the Royal Borough of Kensington and Chelsea and sit immediately to the west of Hyde Pa ...
,
London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
, UK File:Man playing guitar in a portrait with lens flare.jpg, alt=Lens flare example, Lens flare example in picture in a portrait. 50 mm at f1.4 File:MarsPerseveranceRover-Rainbow-20210404.png, Many mistook an April 4, 2021 lens flare on Mars, which appears in a '' Perseverance'' rover photograph, for a rainbow, until NASA clarified the issue. File:Lens flare Bow River trail Calgary, Alberta.jpg, Lens flare in shadow of poplar tree File:LensFlare.jpg, Extreme lens flare caused by intense sunlight File:Optical Ground Station 2.webm, Lens flare in a film clip File:'Perception of Christ Ascending to Heaven' Dome of the Rotunda of the church of the Holy Sepulchre Jerusalem Victor Grigas 2011 -1-19.jpg, Sensor flare—light is reflected off the sensor to the lens and then back to the sensor


See also

*
Anti-reflective coating An antireflective, antiglare or anti-reflection (AR) coating is a type of optical coating applied to the surface of lens (optics), lenses, other optical elements, and photovoltaic cells to reduce reflection (physics), reflection. In typical ima ...
, used to reduce lens flare and produces the red and green colors common in lens flare. *
Bokeh In photography, bokeh ( or ; ) is the aesthetic quality of the blur produced in out-of-focus parts of an image, whether foreground or background or both. It is created by using a wide aperture lens. Some photographers incorrectly restr ...
, a source of circles around out-of-focus bright points, also due in part to the internals of the lens. *
Diffraction spike Diffraction spikes are lines radiating from bright light sources, causing what is known as the starburst effect or sunstars in photographs and in vision. They are artifacts caused by light diffracting around the support vanes of the secondary m ...
, a type of lens flare seen in some
telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
s


References


External links

* {{DEFAULTSORT:Lens Flare Image defects Lenses Optical phenomena