Who’s afraid of lens flare?
One of the eternal threat for photographers of all kinds has always been, and still is, lens flare.
Such a dramatic effect can totally ruin otherwise interesting pictures and, usually, it is only discovered after the shot.
Which is too bad.
But there are times when a well managed flare can add emotion to the scene. For this reason some photographers use special filters to create and control flare, as well as software tools to generate any kind of flare in post-production.
Lens flare is most obvious in dark areas of the image, and it comes in two very different forms: ghosting flare and veiling flare.
In the image of the two girls here at right you get both kinds of flare. They are usually intermingled but otherwise there can also be a prevalence of one over the other.
Ghosting flare (also known as just ghosting) produces weird light spots of possibly many colors, as well as specks, shapes and stripes which may, at times, even cover the whole picture or a consistent portion of it. Halos often reproduce the appearance of the lens aperture in use.
Veiling flare comes in the likelihood of haze: details are softened, contrast reduced, true blacks and shadows turn to any shade of grey or, most often, to muddy colors.
What you find in this page
- Understanding lens flare
- How to avoid lens flare in photographs
- How to create lens flare with camera filters
- How to create lens flare with software filters
Understanding lens flare
There are a few fundamental principles involved in the thing we call lens flare.
None is so important that you cannot make good photographs without learning about them: you can lightheartedly skip to the next section on how to avoid lens flare in photographs, if you like.
Or you can keep on reading, which is what we warmly suggest: there are some funny things connected with reflections and refractions of light, as anybody might have observed when looking at a glass of water.
It is easy to observe light refraction when any object is immersed in a glass of water: the path of light inside water differs from the path of light outside water, so that the pencil (here at left) seems to be broken.
The glass of water, with its rounded shape, acts like a magnifying glass, and the part of pencil immersed in water looks bigger than the other part. Also, if one moves the pencil around the glass, the image changes due to different light angles within water.
The path of light
As a general rule, light rays move along a straight path, unless they bump into something, in which case strange things may happen. Ray can, among other things, be reflected or refracted.
Reflection is when light rays hit a surface and bounce at an angle. In case of specular reflection, the one we all experience in mirrors, all rays are reflected at the same angle. (Image A)
Refraction is a bit more complicated kind of thing. It occurs when a light ray travels into a new material: it changes speed and should the ray hit the surface of the material at an angle, the ray is bent.
The amount of the bending depends on a few variables, among which the angle formed by the ray as it hits the new material, and the characteristic of the material itself.
It is important to note that in real life both reflection and refraction happen at the same time. So, when a light ray enters a piece of glass at an angle and is refracted, still a small amount of light is reflected and, instead of entering the glass, it is bounced back to another direction. (Image B)
The very same happens as the ray hits the second glass surface: part of the ray is refracted and bent as it leaves the glass and meets the air again, while another part (usually smaller) is reflected and bounced back at an angle inside the glass; this latter ray will eventually exit the glass, and again be refracted, of course. (Image C)
A single lens element can be approximated to a prism, somehow.
Stray light is not easily controlled: you can imagine, on any multi-lens optical system (Image D), how many unwanted refractions and reflections are generated by any single ray of light. And it is too clear why it is important to keep any superfluous light ray from hitting the lens.
Parasite light scatters anywhere inside the optical system, and hits the sensor at random, generating an overall haze effect: imagine it is like spraying a thin veil of white paint evenly over a picture. Not only fine details are spoiled, but also contrast is reduced in that white areas remain white, whereas dark areas are turned into a lighter tone.
How much internal reflections reduce contrast depends on
- the amount of glass surfaces
- the quality of the lens coatings
- how light strikes the front lens element
So, the best way to reduce lens flare overall is by reducing the amount of indirect light entering your lens, as well as controlling the in-frame sources of strong light.
How to avoid lens flare in photographs
Here you find 5 hints to help you minimize lens flare.
Keep in mind that other variables can influence the results: aperture is one of them.
Also, if you shoot in Raw format, you could later have more chances to reduce a bit unwanted flare.
If you want to play safe with lens flare, refrain from shooting with backlighting.
You should test your lenses in backlighting conditions in that not two lenses are the same. If you are not lucky enough to own those high quality lenses which can face backlighting without generating horrible flares, then play safe and keep your front lens in a shadow area whenever possible. Be it a tree trunk, a building, or any possible object, let your front lens be shaded from direct light rays.
Modern lenses are produced with thin layers of optical anti-reflection coating applied to the surface, designed to reduce flare. Such a solution is highly effective, but extra care should be taken not to damage the multi-coating when handling the lens. This is particularly true for the front lens, which should not be aggressively cleaned.
Greasy fingers are a double annoyance for lenses: if not cleaned, dirt generates uncontrolled flare, whereas if cleaned there is risk to spoil the multi-coating layers.
Lenses should be protected from dust and dirt whenever possible (read more on UV filters, though).
Flare cannot be avoided when a strong light source is included in the frame: it is there that you can often tell between a good, high-quality lens, and an average one. Also, the more complicated a lens, the more pieces of glass involved, the more likely you will get lens flare of some sort. This is also a reason to prefer prime lenses instead of zooms, at times.
Good lenses today have multiple anti-reflection coatings and can be used in the harshest lighting situations.
The lens hood keeps extraneous light from striking the front lens element of your camera.
Using lens hoods is the best way to avoid or minimize lens flare. A lens hood should always be mountend on any camera lens: it not only reduces flare and increases image contrast, but also physically protects the front lens from hitting other objects.
Check that your lens hood shades the most possible area around your frame.
Double check, though, that it does not interfere with the scene inside your frame: do this by closing the aperture to the intended shooting value, and closely looking for possible vignetting. Also, by inspecting the lens from its front, check that the lens shade covers at least the aperture area, if not the whole front glass of your lens.
Aside from a good lens hood, remember that when shooting the front lens should always be protected by direct light rays: place your camera in the shadow, or even ask somebody to use his/her hand to cast a shadow into your lens.
Lens shades are a key factor at any camera level, from the most basic compact cameras (which often include a shade in their design) through reflex cameras up to the best view camera and lens systems.
Tripods indirectly help avoiding lens flare: having your camera firmly set on a tripod allows you to check and double-check that the lens is properly shaded. Also, you have both hands free in order to shield the front lens from disturbing light rays. Of course, be careful not to pop your hand or objects into the frame.
If you cannot use a tripod, try a beanbag instead, or whatever rig you can happen to find around you: the key issue is keeping the camera steady and still, and have your both hand free at the same time.
Like it or not, UV (Ultraviolet) filters, as well as other supposedly lens protecting filters of any kind, are a cause of flare. Definitely. No matter how good your filter might be, if you seriously care about flare take off UV filters from your lens.
As a general rule, use filters only when there is a strong indication for them: UV can be useful when shooting high in the mountains, and there are cases when real lens protection is a priority.
Keep your cold blood: the more quality and expensive your lens, the better it is to leave any protecting filter off. You would not, otherwise, make justice to such an excellent piece of glass.
How to create in-camera organic lens flare
Although an optical defect and theoretically to be avoided, lens flare is often able to trigger strong emotional reactions within the observer. It is therefore understandable that many photographers (and cinematographers) resort to any ingenious method in order to obtain a (more or less) controllable lens flare effect.
Next to software solutions, there is a variety of physical devices and tricks which can be used to generate flare effects of any sort.
The first and most easy way to get flare on your photographs is obvious: just do right the opposite of what we suggested about avoiding lens flare. So, do not use any lens hood, and whenever possible take care to include a strong source of light inside (or very close to) your frame. Also, use one of those UV/lens protecting filters usually sold and screwed-in the vast majority of photo amateurs cameras, and you are half-way in getting wonderful flare. You can add to it by making your filter a bit dirt, or by smearing a thin layer (or just some spots or stripes) of vaseline on your filter. Be careful not to overdo your effect, or you will just get a blurry/soft/deformed image. Never ever place vaseline on the real lens, of course. The amount of effect of such filters depends on your lens focal length as well as the aperture you set for your shot.
There are hundreds more home-made solutions: a thin nylon/silk tulle netting placed in front of the lens, is one of them.
As an alternative, there are high-quality ready-made filters from the best manufacturers worldwide. You could find many of them at B&H Photo.
How to create lens flare with software filters
The short video at right shows the emotional impact of flare in images.
There is huge amount of products designed to render lens flare of any kind. They range from the most basic one-click no brain effects you can find in some online retouching tools to the astonishing results seen in high-tech Hollywood movies. The key player in the field is Red Giant which also have an interesting selection of very good video tutorials. In-between you have a vast choice of filters capable of adding typical flare halos, rings, stars and lines: many of such filters are also available as free open-source code.
As one may expect, advanced lens flare tools are available for many mobile devices, ranging from iPhone to iPad and beyond.
The risk to overdo with software effects is, honestly, rather high.
All in all, one should really take care not to spoil good images. Two advices for this:
- always have a backup of your original files;
- as yourself why are you adding effects.