Visual flare, often called lens flare, is an optical phenomenon appearing in photographs and videos. It results from non-image-forming light interacting with the camera’s optical system. Flare occurs when a bright light source, such as the sun or a streetlamp, strikes the lens elements and scatters across the image sensor. While often viewed as an unwanted artifact that degrades image quality, it can also be a powerful creative tool for adding atmosphere and drama to a scene.
The Physics Behind Visual Flare
Visual flare originates from the journey of light rays through the multiple glass elements within a lens. When a powerful light source hits the front of the lens, a portion of that light is reflected and scattered internally by the surfaces of the lens elements instead of traveling directly to the sensor.
Light scattering is exacerbated in lenses with many glass components, such as complex zoom lenses, because they feature more glass-to-air interfaces where reflection can occur. Each glass-air boundary reflects a small percentage of light, causing it to bounce across the interior of the lens barrel. Manufacturers combat this effect by applying multi-layer anti-reflective coatings to the lens surfaces, which significantly reduce internal light reflection.
These specialized coatings mitigate reflections, but they cannot entirely eliminate the scattering effect, especially when dealing with extremely intense light sources. The remaining scattered light lands on the camera sensor in an uncontrolled manner, creating the visual effects known as flare. This mechanism is distinct from the light that forms the intended image, which is governed by the lens’s refraction and focusing capabilities.
Distinct Manifestations of Flare
Visual flare typically manifests in two primary forms, each with a distinct visual impact. The first is veiling flare, which presents as a general wash of haze or glare across the entire frame. This effect drastically reduces the overall contrast of the image, causing dark areas to appear faded and colors to look desaturated. Veiling flare often occurs even when the bright light source is positioned just outside the frame but is still shining onto the front lens element.
The second manifestation is ghosting flare, which appears as distinct, bright artifacts within the image. These ghosts often take the shape of the lens’s aperture, appearing as multi-colored polygonal shapes, circles, or streaks of light. Ghosting is caused by light rays reflecting repeatedly between the lens elements before reaching the sensor. These artifacts are usually positioned in a line directly opposite the light source causing the reflection.
Controlling and Utilizing Flare
Photographers and videographers employ specific techniques to either avoid flare or introduce it intentionally. The most common avoidance method is using a lens hood, a physical attachment that extends from the front of the lens to block stray light from hitting the glass elements at oblique angles. If a lens hood is insufficient, the camera operator can physically shield the lens with a hand or opaque card, blocking the light source without entering the field of view.
Adjusting the camera’s position is another strategy, often by slightly repositioning the camera so the light source is blocked by an object within the scene, such as a tree or a building. Conversely, flare can be utilized creatively to enhance the mood or atmosphere. Positioning the light source at the edge of the frame allows a controlled amount of flare to spill into the shot, creating a warm or dreamy aesthetic.
The shape of the ghosting flare can also be controlled by adjusting the lens’s aperture setting. Shooting with a wide aperture produces a softer, more subtle halo-like flare, often desirable in portraiture. Using a narrow aperture causes the flare to take on a more defined, starburst shape, which adds dramatic effect to shots featuring lights at night.