What is lens flare? Ghosting, blown-out highlights, crushed shadows and vignetting explained

Point your camera towards the harsh Highveld summer sun and the result can be a frame washed out with haze, dotted with coloured shapes or split between pure white and solid black. If you are new to photography, it is easy to assume something is wrong with your camera. In most cases, though, these effects are not faults at all but natural results of how lenses and sensors handle light. This guide explains what causes lens flare, ghosting and related effects, how to control them and how to use them to your advantage.

A photograph that uses ghosting creatively

Lens flare and other effects that change image quality

The way cameras and lenses handle light can produce effects you did not intend. The most common are:

•        Lens flare, where strong light washes out the image and lowers contrast

•        Ghosting, where rings, ovals or aperture-shaped spots of light appear in the frame

•        Vignetting, where the corners of the image turn darker than the centre

•        Blown-out highlights, where bright areas turn pure white and lose detail

•        Crushed shadows, where dark areas turn solid black and lose detail

Each of these can lower image quality, but each can also be prevented. They are not always a problem, either: used deliberately, they can add atmosphere and emphasis. Understanding their causes is the key to controlling them.

Lens flare and ghosting: effects caused by the lens itself

Every lens is built from several glass elements, and the way light travels through them gives rise to two closely related effects: lens flare and ghosting.

What is lens flare?

Lens flare occurs when strong light enters the lens and scatters inside it, spreading a veil of haze across the image. Contrast drops, colours fade and the whole frame can look milky and soft. It is most likely when you shoot towards the sun in backlit conditions, and the harsh sun of a Highveld summer afternoon can easily produce it if light strikes the front of the lens. How strongly flare appears depends on the lens design and coatings, but any lens can flare under the right conditions.

What causes lens flare?

The main cause is a bright light source, usually the sun, shining directly into the lens. Light that should pass straight through to the sensor is instead reflected and scattered between the glass elements, and every extra bounce reduces clarity. Light striking the front element at an angle is particularly troublesome. Dust, smudges and fingerprints on the lens surface make things worse by scattering light even further.

How to reduce lens flare

The simplest defence is a lens hood, which blocks stray light from the sides and above before it reaches the front element. It is worth fitting one whenever you shoot outdoors in strong sun. Even a small change in the camera’s angle or position can move the light source enough to make a noticeable difference.

Lens coatings play a major part too. Multi-layer anti-reflection coatings, such as TAMRON’s BBAR-G2 (Broad-Band Anti-Reflection Generation 2), reduce reflections on lens surfaces and help keep images clear even in backlight. Finally, keep the front element clean, as a quick wipe with a proper lens cloth can restore lost contrast.

What is ghosting?

Ghosting appears as distinct shapes of light, such as rings, ovals or polygons, caused by light reflecting between the surfaces inside a lens. It is common in scenes with strong point light sources, whether the sun by day or Johannesburg’s street lights after dark. Ghosting shares its cause with lens flare, but rather than hazing the whole frame, it creates clearly defined patterns in specific parts of the image, often in a line running from the light source through the centre of the frame.

What causes ghosting?

Ghosting comes from light bouncing between the many glass surfaces inside a lens. Each element has a front and a back surface, and every surface can reflect a small amount of light back towards the sensor. Lenses with more elements, including many zooms, have more surfaces where this can happen, although modern coatings have greatly reduced the effect. The shape of a ghost often mirrors the aperture: a rounded aperture produces round ghosts, while a polygonal one produces polygon shapes. Filters add further surfaces, so light can also reflect between a filter and the front element.

How to reduce ghosting

Good lens coatings are the first line of defence, and anti-reflection technology has advanced considerably in recent years. Composition matters too: keeping strong light sources just outside the frame avoids most ghosting, and if you do include the sun, shifting your angle slightly can move or shrink the ghosts. A lens hood helps here just as it does with flare.

Filters deserve attention as well. Stacking several filters multiplies the reflective surfaces and makes ghosting more likely. If you notice ghosts while using a polariser on the Cape coast, for instance, try removing the filter to see whether they disappear.

Using lens flare and ghosting creatively

Lens flare and ghosting are not only flaws. Introduced deliberately, they can add a dreamy, atmospheric or emotional quality to an image and work well as visual accents. Here is how to use them in three common types of photography.

Portraits

A portrait using ghosting and lens flare

In portraits, flare and ghosting can create a striking, romantic mood. Position your subject with the sun behind them near sunset, such as on a West Coast beach, and include the sun at the edge of the frame so soft light spills around them. The same backlight creates a rim of light along hair and shoulders, separating the subject from the background and adding warmth to the scene.

Landscapes

A landscape using ghosting

At sunrise and sunset, including the sun in the frame introduces flare that gives a landscape a luminous, atmospheric feel. During a Drakensberg sunrise, for example, flare and ghosting can emphasise the first light spilling over the peaks, while shafts of light breaking through valley haze add depth. On foggy or overcast days, such as when sea fog rolls along the Garden Route, the diffused light creates a softer, quieter atmosphere.

Street snaps

A street snap using ghosting and lens flare

Flare and ghosting can add an emotional touch to everyday scenes. Photographing people as silhouettes against the backlight, with a touch of flare, gives a warm, nostalgic feel; when children are in the frame, ask a parent or guardian first. In the city, sunlight bouncing off the glass towers of Johannesburg, combined with ghosts from street lamps, can capture the distinctive character of an urban setting.

Beyond lens flare: blown-out highlights, crushed shadows and noise

Exposure is one of the fundamentals of photography, but every camera sensor has limits. The range of brightness it can record, known as dynamic range, is finite: tones brighter than the upper limit turn pure white, while tones darker than the lower limit turn solid black. Here is how each effect arises and what to do about it.

What are blown-out highlights?

A photograph using blown-out highlights

Blown-out highlights occur when overexposure pushes bright areas beyond what the sensor can record, so they turn pure white and lose all detail. The risk is highest in strong daytime sun and in night scenes with bright light sources such as street lamps. Once detail has been lost, it is difficult to recover even in editing, so it is best to prevent it at the time of shooting.

Seen differently, blown-out highlights can be a creative tool. A deliberately bright, high-key image against a white background, as in the example above, can make the subject stand out and create a soft, fresh mood. The bright white sand of the beaches around Cape Town lends itself naturally to this style.

How to prevent blown-out highlights

Setting exposure compensation to the negative side is the most direct fix, reducing overall brightness so highlights hold their detail. Many cameras also offer a highlight-weighted metering mode, and spot metering on the brightest important area achieves a similar result. Check the histogram as you shoot: a graph pressed against the right-hand edge is a warning sign. For important shots, shooting in RAW gives you more room to recover highlights during processing.

What are crushed shadows?

A photograph using crushed shadows

Crushed shadows, sometimes called crushed blacks, occur when underexposure pushes dark areas below what the sensor can record, so they become solid black and lose detail. They are most common in low light, whether in deep shade, a dim interior or a night scene, and they flatten the texture and form of the subject. As with blown-out highlights, lost shadow detail is hard to restore fully in editing.

Used deliberately, however, crushed shadows can be highly effective. Rendering a subject as a black silhouette against a sunrise sky, such as the Indian Ocean dawn over Durban, intensifies the colours of the sky and creates a dramatic image.

How to prevent crushed shadows

Setting exposure compensation to the positive side brightens the image and lifts shadow detail. Spot metering on an important dark area is another option. You can also add light to the shadows with a flash, a small LED panel or a reflector. If you shoot in RAW, you will have more flexibility to open up the shadows during processing.

What causes noise, and how can you reduce it?

Noise is another exposure-related effect worth understanding. It appears as a grainy, speckled texture across the image and becomes more visible as ISO sensitivity rises. It often shows up when you raise ISO to keep a fast shutter speed in dim conditions, such as indoor netball in a Gauteng sports hall or an evening braai under string lights.

Modern interchangeable-lens cameras handle noise far better than earlier models, but if you want to keep fine detail crisp, an upper limit of around ISO 3200 to 6400 is a sensible starting point, depending on your camera. To gather more light without raising ISO, use a lens with a wide maximum aperture (a small F-number), or mount the camera on a tripod so you can use a slower shutter speed.

Vignetting: when lens design and lens flare accessories darken the corners

Some effects depend on the equipment itself and how it is set up. Vignetting is the most common, and it can come from the lens design, from the combination of lens and camera, or from accessories such as the hoods and filters used to control lens flare.

What is vignetting?

Vignetting is a darkening of the image towards its corners: the centre stays bright, while the edges become gradually darker. There are two main types. Optical vignetting, also called light fall-off, is a natural characteristic of many lenses, especially wide-angle lenses used at their widest apertures. Mechanical vignetting occurs when something physically blocks light at the edges of the frame, such as a hood, a filter or a lens whose image circle is too small for the sensor.

Mild vignetting is often barely noticeable, but it can be a problem when you need even brightness across the whole frame, as in architecture or landscapes such as rows of vines receding across the Winelands. In extreme cases of mechanical vignetting, the corners can turn completely black.

What causes vignetting?

Optical vignetting arises because light reaching the corners of the sensor travels at a steeper angle and is partly obstructed within the lens barrel, so less of it arrives. It is strongest at wide apertures and usually reduces as you stop down.

Mechanical vignetting has several common causes. Fitting a lens designed for APS-C sensors to a full-frame camera means the image circle does not cover the whole sensor, leaving dark or black corners; many mirrorless cameras avoid this by switching automatically to an APS-C crop mode. A lens hood that is fitted crookedly, or the wrong hood for the lens, can intrude into the frame, particularly with wide-angle lenses. Stacking filters can have the same effect, as their rims narrow the field of view at the edges.

How to prevent vignetting

Make sure your lens hood is the correct one for the lens and that it clicks fully and straight into place. When using a camera’s built-in or pop-up flash, remove the hood, as it can cast a shadow at the bottom of the frame.

With filters, choose slim-profile designs and avoid stacking several thick filters, especially on wide-angle lenses. For optical vignetting, stopping down by a stop or two usually evens out the corners, and many cameras and editing programs offer automatic lens corrections.

Using vignetting creatively

Vignetting can also be used on purpose, to create a retro or nostalgic feel or to draw attention to the subject. Darkened corners lead the eye naturally towards the centre of the frame, so in a portrait, placing the subject centrally and letting the edges fall slightly darker directs attention to the person.

This vignette effect also lends an artistic, vintage character to subjects with a sense of history, such as antiques, retro furniture and period interiors. The Art Deco façades of Durban are a good match, where a gentle vignette complements the era of the architecture.

Controlling lens flare, ghosting and exposure in your photography

Lens flare, ghosting, blown-out highlights, crushed shadows and vignetting all have clear causes, and once you understand them, you can prevent them with the right lens, accessories and exposure settings. The same knowledge lets you use them deliberately to add atmosphere and emphasis. Try a simple exercise: photograph a backlit scene with and without a lens hood, then compare the results. It is the quickest way to see how much control you really have.