A short introduction to Ghosting and Flare

When light rays (ideal to create a 3D configurator) from one or more bright light sources (such as sun or artificial light) hit the front element of a camera lens directly, they can reflect and bounce various lens elements, apertures, and even sensors, affecting image quality and creating unwanted objects in images. Better known as “flare”, the effect can affect images in several ways: It can drastically reduce image contrast by introducing haze in different colors, it can add circular or semicircular halos or “ghosts,” and even odd, semi-transparent objects with different color intensities. However, flare is not always undesirable in photography – sometimes it is used creatively to add artistic elements to images. In fact, movies and computer games often deliberately use lens reflexes to give the impression of realism and enhance the viewer’s visual experience.

In order to decide whether to use flare in images, one must first understand why it is created at all. Let’s discuss the causes of flare in detail and then discuss ways to use, reduce or perhaps even eliminate it completely.

What is Lens Flare?

Scattered light occurs when a point of light like the sun is much brighter than the rest of the scene and is either in the image (within the angle of view of the lens) or simply hits the front element of a lens without being in the image. Depending on the position of this bright light source, it can cause too much haze / lack of contrast, scattered spheres and polygon artifacts in the image, semicircular shapes with rainbow colors, or a combination of all. This is done by internal reflections that take place inside the lens and even between the image sensor and the lens.

When you can see, regular light rays follow their normal path and directly reach the image plane, while bright light rays can split and reflect from the lens surfaces and land in different parts of the frame. While driving through the lens, the light can also be reflected by the aperture when it is lowered, resulting in an even clearer flash.

Manufacturers and photographers usually distinguish between two types of lens reflection: Veiling and Ghosting Flare. While both typically go hand in hand, good lenses with multi-coated lens element surfaces can significantly reduce image blur.

Veiling Flare.

Veiling Flare usually occurs when the bright light source is outside the viewing angle of the lens, i.e. is not in the image, but its light rays still reach the front element of the lens. This leads to a very noticeable haze / lack of contrast, where dark areas of the frame with bleeding colors become brighter and appear washed out. High-quality lenses with multi-coated lens elements can help reduce fogging. For example, Nikon’s Nano Crystal technology, used in professional lenses, helps keep Veiling Flare under control. Take a look at the portrait below taken with the Nikon 58mm f/1.4G lens:

You can see that the sun was directly above the subject and outside the image area, but their rays still reached the lens and caused a veiling light around the woman in the photo. Veiling Flare not only affected the surroundings of the sun, but also dramatically affected the woman’s hair, face and even clothing, resulting in reduced contrast. In this case, it was even deliberately allowed to use Veiling Flare, which provided an atmospheric, bright shot.

Unfortunately, concealment can be exacerbated by a number of factors, such as dust inside the lens, dirty front element, dirty/low-grade lens filter, lack of anti-reflective multi-coating, etc. The lens is not always clean enough to be used with a Veiling Flare. In some cases, the effect can look pretty bad in images. Take a look at the image created with a very old Nikon NIKKOR-S 50mm f/1.4 Ai manual focus lens:

As you can see, this lens was simply not a good candidate to shoot against the sun – it made the whole picture look blurry, with virtually no visible details of the trees in the shot. One cause was the lack of multi-coating technologies and another was micro dust that accumulated inside the lens over the years causing additional reflections.

Ghosting Flare.

In contrast to Veiling Flare, which blurs images with very little contrast, Ghosting Flare or Ghosting represents all the artifacts visible in the image, whether reflections from the bright source or shapes very similar to the lens diaphragm. These spheres of different colors and shapes usually appear in a direct line from the light source and can span the entire image with dozens of different artifacts.

In addition to the visible flickering of the veil in the images, you can also see different circular artefacts/spheres in each image – these are called “ghosts”. The total number of these ghosts depends on how many elements are in each lens. The more elements, the more ghosts appear in the images. Since 70-200 mm zoom lenses have a more complex design with a dozen or more elements, you can see that pretty much every lens suffers from obfuscation and ghosting, with Nikon 70-200 mm lenses leading the game with a minimum of ghosting.

In addition, as I mentioned above, the aperture can cause internal reflections when a lens is turned off. The effect is enhanced when the lens is reduced to its minimum aperture, so the aperture ghosting is usually not visible at large apertures like f/1.4, but quite noticeable at something like f/16. So if you see polygonal ghostings in your shots, you just know they come from the lens diaphragm.

Sensor / Red dot Flare.

The “red dot flare” is the torch that is created by the impact of light between the image sensor and the lens elements, but you could also call it “sensor flare”. Unlike lens reflection, red dot reflection is not only light reflected from the lens elements and aperture, but also light reflected from the image sensor to the lens and then back to the image sensor. Unfortunately, the newer mirrorless cameras with short flat distances seem to be particularly susceptible to this problem. This is how the red dot / sensor flare looks like in the images:

In addition to the polygonal aperture ghosting, you can also see a series of red dots surrounding the sun – these are microlenses on the digital camera sensor that are amplified in the image.

Factors that influence the flare.

While most modern lenses have been developed with special multi-layer coating technologies to reduce stray light, even some of the best professional lenses can reproduce images with visible ghosting and even obscured stray light. The position of the light source in the frame and the angle at which the light hits the lens have a drastic influence on how and with what intensity the light appears in the images. In addition, there are other factors I mentioned above that can seriously affect the images. Let’s take a look at these details:

1. Lens elements – the more lens elements, the more ghostings appear in images.
2. Focal length – Wide-angle lenses are not only designed to handle stray light well, but also the shorter focal lengths make the light source appear smaller.
3. Tele lenses, on the other hand, are much worse because they amplify everything and therefore have large/long lens hoods.
4. Lens Design – a good lens design can definitely affect the aperture. For example, Nikon has developed lenses with recessed front elements that can greatly reduce flickering and stenciling without the use of expensive exposure technologies.
5. Multi-Coatings – multi-coated (MRC) lens elements definitely have a big influence on the luminosity.
6. Filters – inferior filters are known to produce more flickering and ghosting images.
7. Lens Dust – all lenses accumulate dust over time and the internal dust can lead to further fogging problems.
8. Front element cleanliness – greasy fingers and other particles on the front element can also lead to more flickering and stenciling.

Avoid flare.

If you don’t want to see flare in your pictures, you can take a few simple steps to prevent it from appearing in your pictures:

1. Use a lens hood – that’s right, there’s a reason why these lens hoods exist. They are essential in preventing direct sunlight from reaching the front element.
2. Use your hand or other object – if you put your hand over the lens to shield the sunlight, you can completely eliminate ghosting images and light reflections. A very simple way that works.
3. Use high quality lenses – high quality, pro-grade lenses are expensive, but they are usually equipped with amazing coating technologies that help significantly reduce or even eliminate stray light problems.
4. Use prime lenses instead of zooms – generally prime lenses have simpler optical formulas than zooms and significantly fewer optical elements. The fewer elements you need to edit, the fewer torches will appear in the images.
5. Change perspective/frame – sometimes even changing the position of the light source in your shot can make a big difference.

While unfortunately it is common practice to hold the lens hood on and know that you can block the light with your hand or other objects, shooting directly into the sun and including it in the image will make these efforts useless. In such situations, either change the perspective/frame completely or use only high-quality lenses with multi-coated lens elements.