What Is Lens Flare?
Lens flare is a non-image-forming artifact that occurs when light from a bright source, most commonly the sun, scatters and reflects between the glass elements inside a camera lens. Every photographic lens is a multi-element optical system, and each air-to-glass surface is a potential point of internal reflection. When stray light bounces between these surfaces instead of following the intended optical path to the sensor, it manifests as visible artifacts: bright streaks radiating from the source, polygonal ghost shapes distributed across the frame, or a diffuse veiling haze that lowers overall contrast.
For decades, lens flare was treated exclusively as an optical defect to be minimized through lens hood use, anti-reflective coatings, and careful framing. Lens designers at companies like Canon, Nikon, and Zeiss invested considerable engineering in multi-layer coatings to suppress internal reflections. The perspective shifted in the 1960s and 1970s when cinematographers began deliberately incorporating lens flare for atmospheric effect. Today, lens flare occupies a dual identity in photography: it is both a technical flaw to manage and a creative tool to deploy.
Before anti-reflective coatings: Early photographic lenses used uncoated glass elements. Each air-to-glass surface reflected approximately 4 to 8 percent of incoming light back into the optical path. A lens with 6 elements and 10 air-to-glass surfaces could lose 35 to 55 percent of light transmission to reflections, producing severe flare and low-contrast images in any backlit scenario. After modern coatings: Contemporary multi-layer coatings reduce per-surface reflections to 0.1 to 0.5 percent, bringing total reflection losses in a 15-element zoom lens down to approximately 2 to 5 percent. The improvement is dramatic but does not eliminate flare entirely, especially when a bright source sits at the edge of the frame or within the lens’s field of view.
How It Works
Lens flare takes two primary forms: veiling flare and ghosting. Veiling flare is a broad, uniform scattering of light across the image plane that reduces contrast without creating distinct shapes. It occurs when light bounces multiple times between elements and spreads diffusely. The effect is similar to looking through a dirty window toward a bright light: the overall image appears washed out. Veiling flare can reduce the effective dynamic range of a scene by 1 to 3 stops, lifting shadow values and compressing the tonal range.
Ghosting produces distinct, visible artifacts. Each ghost is a reflected image of the light source, shaped by the aperture diaphragm of the lens. A lens set to f/16 with a 7-blade diaphragm produces heptagonal ghost shapes. At f/2.8, where the aperture is nearly circular, ghosts appear as round discs. The number and distribution of ghosts depend on the number of lens elements. A prime lens with 7 elements may produce 3 to 5 visible ghosts. A complex zoom with 18 to 23 elements can generate a dozen or more, arrayed in a line extending from the light source through the center of the frame and out the opposite side.
The position of the light source relative to the lens axis determines flare intensity. When the source is centered in the frame, light travels close to the optical axis and encounters fewer oblique reflections, often producing less flare than when the source is near the frame edge. Sources positioned 10 to 30 degrees outside the frame but still able to strike the front element produce some of the most intense veiling flare because the light enters at steep angles that maximize surface reflections.
Aperture choice directly affects flare character. Stopped-down apertures like f/16 or f/22 produce defined starburst patterns from the light source itself, caused by diffraction at the aperture blade edges. A lens with 8 straight blades produces an 8-point star. A lens with 9 blades produces 18 points because odd-numbered blade counts double the ray count. Wide apertures minimize the starburst effect but can increase the visibility of circular or ring-shaped ghosts.
Practical Examples
Landscape photography with intentional sun flare. A photographer frames a mountain scene with the sun partially obscured by a ridge line. At ISO 100, f/16, 1/250 s, the 8-blade aperture produces a crisp 8-point starburst radiating from the sun’s position. Partially hiding the sun behind a solid object, a technique called “sun peeking,” concentrates the flare into the starburst while preventing the broad veiling haze that would occur if the full solar disc were visible. This approach has become a signature of wide-angle landscape photography.
Portrait photography with backlit haze. Fashion and lifestyle photographers sometimes shoot into the sun at golden hour with the subject between the camera and the light source. Using a vintage or uncoated lens at f/2.8, the resulting veiling flare lowers contrast across the entire frame, producing a warm, dreamy haze that wraps around the subject. A Canon FD 50mm f/1.4 from 1971, with single-coated elements, produces substantially more veiling flare than a modern Canon RF 50mm f/1.2 L with ASC nano-coating, making vintage lenses popular choices for this deliberate effect.
Astrophotography and night scenes. Bright point sources like streetlights and the moon can produce pronounced ghosting in night photographs. A 14mm f/2.8 wide-angle lens capturing a cityscape with scattered streetlights may show hexagonal or circular ghosts mirrored from each light source. Night photographers who want clean images use lens hoods, flag stray light with their hands, or composite multiple exposures with different light source positions to remove ghosts in post-processing.
Cinematic lens flare. The deliberate use of lens flare in cinema, popularized by directors including J.J. Abrams, relies on anamorphic lenses whose cylindrical elements produce distinctive horizontal blue streaks. Standard spherical photographic lenses do not replicate this effect naturally, but some photographers use anamorphic adapter elements or streak filters to approximate the look. The anamorphic flare streak is caused by the elongated internal reflections within the cylindrical element surfaces unique to anamorphic optical designs.
Advanced Topics
Lens coatings are the primary engineering defense against flare. Single-layer magnesium fluoride coatings, introduced commercially by Carl Zeiss in 1935, reduce per-surface reflections from approximately 4 percent to 1.5 percent. Modern multi-layer coatings stack thin films of alternating high and low refractive index materials, each tuned to a specific wavelength band, reducing reflections to below 0.2 percent per surface. Nikon’s Nano Crystal Coat, Canon’s ASC (Air Sphere Coating), and Sony’s Nano AR Coating II represent current state-of-the-art approaches, each using slightly different material science to achieve similar results.
The internal barrel of a lens also plays a role. Poorly designed lenses may have shiny internal surfaces that reflect stray light toward the sensor. High-quality lenses use matte black coatings, flocking material, or ridged internal baffles to absorb stray light before it reaches the optical path. The quality of these internal treatments is one reason why two lenses with identical element counts and coating technology can exhibit different flare characteristics.
Sensor reflections contribute a secondary source of flare unique to digital photography. Light that passes through the lens and strikes the sensor can reflect off the sensor’s surface back toward the rear lens element, then reflect forward again to the sensor. This double-pass path creates faint ghost images that were absent in film photography because film’s surface was far less reflective than a glass-covered digital sensor. Some camera manufacturers apply anti-reflective coatings to the sensor’s cover glass to mitigate this effect.
Filters attached to the front of the lens introduce additional air-to-glass surfaces and can exacerbate flare. A UV or protective filter adds two surfaces, each reflecting approximately 0.5 to 1.5 percent of light depending on coating quality. In controlled tests, adding an uncoated UV filter to a multi-coated lens has been shown to increase veiling flare by 5 to 15 percent in backlit conditions. Multi-coated filters minimize this penalty, and many photographers remove protective filters entirely when shooting toward bright light sources.
Post-processing can both add and remove lens flare. Removing unwanted ghosts involves cloning or content-aware fill, though veiling flare requires contrast and black-level adjustments that affect the entire image. Adding artificial flare in editing software involves overlaying rendered flare elements, a common practice in commercial retouching and video post-production. Software-generated flare often appears too uniform and symmetrical compared to optical flare, and experienced viewers can distinguish real from synthetic artifacts.
ShutterCoach Connection
ShutterCoach identifies lens flare in your submitted images and evaluates whether it serves or undermines your composition. The AI distinguishes between intentional creative flare that adds atmosphere and uncontrolled flare that degrades contrast and obscures your subject. When flare is detracting from an image, ShutterCoach recommends specific corrective measures such as adjusting your angle to the light source, using a lens hood, or modifying your aperture to control the flare’s character and intensity.