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Lens flare tutorial


Understanding lens flare


Who’s afraid of lens flare?

Two girls and the sun - strong lens flare — photo by Alex Dram

Two girls and the sun - strong lens flare ©Alex Dram

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

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.

Refracted pencil image — photo by Mohammad Tajer

Refracted pencil ©Mohammad Tajer

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

Specular reflection

©kirpi.it A) Specular reflection




Light refraction

©kirpi.it B) Refraction and reflection




Prism reflections and refractions — photo by Humuku

C) Light path in prism ©Humuku




Prime lens catout — photo by Janne Moren

D) Multiple glasses lens ©Janne Moren

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)

Lenses

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.

Backlighting

Porta Palatina - Torino - Italy — photo by atzu

©atzu Porta Palatina - Torino

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.

Lens coating

Leans coating of a fisheye — photo by Steve Jurvetson

©Steve Jurvetson Leans coating

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.

Lens shade

Lens hood on place — photo by William Murphy

©William Murphy Lens hood

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.

Tripod

Camera on tripod — photo by Bill and Nelle

Camera on tripod ©Bill and Nelle

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.

UV filters

Ultraviolet Filter — photo by Andrew_B

UV - Ultraviolet Filter ©Andrew_B

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

Lens flare software is even available for mobile devices

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.

©kirpi.it For a slightly more dramatic effect, lens flare (at right) can be added to images by means of software tools.





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Comments

  1. By Nicolas, on November 12, 2010, at 01:57 PM
    Very good tutorial. Thanks a lot for this nice job!
  2. By Daniela, on February 05, 2011, at 11:37 AM
    I seldom leave comments on blogs, but I have been to this post which was recommended by my friend, lots of valuable details, thanks again.
  3. By Micah Spanner, on September 12, 2011, at 09:23 PM
    Hi, I’m a hobbyist photographer, and I’ve been wondering for some time about where to find an online photo editor with an adequate effect to add lens flare. I found your site and was excited to find the best program for this but everything I’ve tried seems to come to no avail. What’s your suggestion for the best online software to add lens flare?
  4. By kirpi, on September 12, 2011, at 09:50 PM
    First and foremost: lens flare is a very mutant beast. There is no “standard” lens flare, and you can enjoy yourself by changing lens and settings and see how many variations you can get (of course, there is much more, this is just a tiny example, in order to make clear that you can really go free and creative with lens flare effects). As an example, you could create (or find online) the effect you like and place into your image as a layer.
    More strictly answering your quesion, Micah, and as far as I can say, there is no real (read: serious) lens flare effect online software available. I’ve already linked to LunaPic as a mild (read: very basic) example. But you will not find a lot more as a web-based solution today.
    Such effects are usually both computing-intensive and only required by advanced users, who will thus prefer to work with offline software. In this case both Gimp (free open-source) and Photoshop (not free), just to name some, have their own (and a lot of different) specific tools.
    The best tools though, as mentioned in the article, are from Red Giant Software (there is a lot of work there from John Knoll, the one behind the roots of Photoshop itself, just to give an idea). Still Red Giant Software goes far beyond the real need of a general photographer. And it is very costly software.
    In case you are looking for a specific effect, please let us know (maybe also post an example picture): we will try and help as best as we can :-)
  5. By Micah, on September 14, 2011, at 03:04 AM
    Oddly enough, while I was anticipating an answer to my question, I toyed a little with the layering on Pixlr and found that ripping a free image of lens flare itself on a black background and integrating it with my own flare-free image, I was able to yield a suitable effect. So for other readers who come upon this quaint little web base, If you’re an amateur looking for lens flare effects without coughing up too much money for the programs, this may be your hot ticket. :] thanks for the tips, kirpi
  6. By Pauline Petsel, on February 15, 2012, at 09:54 PM
    I am an amateur photographer and we have had strange things flashing around the sky at night for months and months. I’ve been trying to photograph them and have gotten some very strange stuff. I have a D300 Nikon camera set on a vibration controlled tripod and use a shutter release cord. Last week there was a huge circle around the moon. I took it because it was beautiful. I actually got a funny shot. There is a ‘light bulb’ sitting on top of the moon. It makes a good conversation piece……”The moon just had an idea”.. “Now we know where the moon gets it’s light”…”I wonder what wattage it uses?” ..I wonder how much that utility bill is”. Well naturally the logical answer would be it’s lens flare….but…I’ve also been getting this other stuff that’s strange…Would lens flare be ON TOP of the object?…I looked back on the other pictures I took. The one just has the moon as it should be…another has the very same ‘light bulb’ image but just ‘off’ the moon and on the right of the top.

    My question is ….can a ‘lens flare’ be a same design in two different pictures? what if.. the moon might have moved a fraction or the camera was turned a little?…They were taken within less than a minute of each other…maybe even seconds. Someone told me it was lens flare…I just didn’t think the same exact image would show like that. I’d appreciate you taking your precious time to answer a dummy’s question. I don’t know where to ask and happened on your web sight.

    On top of that one, the person also told me another strange image was a lens flare from bright lights. I had taken a night picture of a beautiful scene below me…The dark silhouetted mountains, dark blue sky and lights coming from the farm houses. I got exactly what I wanted with three. but when I looked back on the one there was a huge ‘pink’ draped looking sheet like thing, hanging in mid air. When I cropped in on the ‘pink’ image the top and one side looked like it was on a sturdy ?pole or stick? then the bottom looked like a depth going back. Also on the left hand corner was something that looked like it was poking through the material! How in the heck could a ‘lens flare’ do that!~? This person is a researcher so I figure they must know but it doesn’t make sense…and ‘they’ aren’t a photographer! Can YOU help by answering the questions? Thank you
  7. By kirpi, on February 15, 2012, at 10:01 PM
    You question is not dummy at all, Pauline :-)
    As a general approach, flare comes in so many different forms and it is so much variable from shot to shot, that you cannot easily foresee or guess the results.
    I would be very glad to help. The only true, real and honest way to give you serious answers would be to closely look at your images. Would it be possible for you to show us your original photographs: full size, straight out of the camera, please? You can post their url here, in case they are available anywhere on the internet, or you can also send them to me by email, and I will take the care to post them here on your behalf.
  8. By kirpi, on February 19, 2012, at 11:33 AM
    Pauline, thank you for providing some of your images by mail: I am posting a couple of them here for everyone’s benefit.

    Light bulb ghost on the moon

    I cannot say too much about your photos, as you sent me just very low resolution pictures (as opposed to the hi-res originals out of the camera, most suitable in such cases).

    Countryside at dusk

    Strange presence in the sky

    Yet one thing is sure: all the “strange stuff” you can see is nothing but lens flare. Definitely.
    To which you might want to add variable amounts of those optical phenomena such as Tyndall effect, Rayleigh and Mie scattering, and more, of course.
    As we’re on this subject, keep in mind that, although it may not apply here, “ghost” shapes might optically (as opposed to digitally) be added to images not only thanks to lens flare effects but also by means of “simple” glass reflections of objects and/or light sources next or even behind the camera (i.e. when shooting from within a closed window). This creates tricky effects which may (or may not) gain further relevance due to a certain amount of blur.
    All in all, from the evidence you provided, there is nothing “strange” in your pictures.
    Pauline, lens flare is nothing but light.
    And as long as you are dealing with photographs, that is as long as you are in the realm of light generated images, the most amazing things will happen!
    :-)




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