What is Distortion?

In photography, there are two types of distortions: optical and perspective. Both result in some kind of deformation of images – some lightly and others very noticeably. While optical distortion is caused by the optical design of lenses (and is therefore often called “lens distortion”), perspective distortion is caused by the position of the camera relative to the subject or by the position of the subject within the image frame. And it is certainly important to distinguish between these types of distortions and identify them, since you will see them all quite a bit in photography. The goal of this article is to explain each distortion type in detail, with illustrations and image samples.

1) Optical Distortion

In photography, distortion is generally referred to an optical aberration that deforms and bends physically straight lines and makes them appear curvy in images, which is why such distortion is also commonly referred to as “curvilinear” (more on this below). Optical distortion occurs as a result of optical design, when special lens elements are used to reduce spherical and other aberrations. In short, optical distortion is a lens error.

There are three known types of optical distortion – barrel, pincushion and mustache / moustache (also known as wavy and complex). Let’s examine each in more detail, but before we do that, let’s take a look at a lens with zero distortion:

No Distortion

Such “perfect” lenses are very rare, since most lenses suffer from at least one kind of distortion defined below. Very good lenses have lens elements that significantly reduce distortion, where it is not noticeable to our eyes. Many zoom lenses, especially superzooms like Nikon 18-200mm VR suffer from multiple types of distortion such as barrel and pincushion at different focal lengths.

1.1) Barrel Distortion

When straight lines are curved inwards in a shape of a barrel, this type of aberration is called “barrel distortion”. Commonly seen on wide angle lenses, barrel distortion happens because the field of view of the lens is much wider than the size of the image sensor and hence it needs to be “squeezed” to fit. As a result, straight lines are visibly curved inwards, especially towards the extreme edges of the frame. Here is an example of strong barrel distortion:

Barrel Distortion

Note that the lines appear straight at the very center of the frame and only start bending away from the center. That’s because the image is the same in the optical axis (i.e. the center of the lens), but its magnification decreases towards the corners.

Barrel distortion is typically present on most wide angle prime lenses and many zoom lenses with relatively short focal lengths. The amount of distortion can vary, depending on camera to subject distance. Even standard 50mm prime lenses can potentially yield barrel distortion at close distances. Barrel distortion can be decreased significantly by using compensating optical elements, but completely eliminating such distortion is nearly impossible. Some lenses like Nikon 14-24mm f/2.8G have a number of such distortion compensating elements, which heavily increase both the weight and the size of the lens. This is why wide-angle lenses are typically bigger and heavier than standard / normal lenses.

Fixing barrel distortion is usually a pretty straightforward process. Post-processing software such as Lightroom and Photoshop, as well as many other third party tools, can easily fix barrel distortion issues, as long as the lens has a supporting profile in the database. Since every lens is different, such lens profile data must be carefully tested in a lab environment and created. I wrote a detailed article that outlines this process in my Lightroom Lens Corrections article.

1.2) Pincushion Distortion

Pincushion distortion is the exact opposite of barrel distortion – straight lines are curved outwards from the center. This type of distortion is commonly seen on telephoto lenses, and it occurs due to image magnification increasing towards the edges of the frame from the optical axis. This time, the field of view is smaller than the size of the image sensor and it thus needs to be “stretched” to fit. As a result, straight lines appear to be pulled upwards in the corners, as seen below:

Pincushion Distortion

Pincushion distortion is also a very common aberration, especially on zoom lenses. Expensive super telephoto prime lenses have compensating elements that can significantly reduce pincushion distortion to negligible levels, but most consumer and even pro-level zoom lenses like Nikon 80-400mm VR suffer from pincushion distortion. In fact, pincushion distortion can be very heavy on consumer-grade lenses, something that you will quickly notice in images.

It is important to note that most zoom lenses that go from wide angle to standard or telephoto focal lengths typically suffer from barrel distortion at the shortest focal lengths, which gradually transitions to pincushion distortion towards the longest end. A good example of such behavior is the Nikon 18-300mm VR, which starts out with strong barrel distortion at 18mm, then quickly switches to pincushion distortion at 28mm and stays that way till 300mm.

Just like barrel distortion, pincushion distortion can also be easily fixed in post-processing software like Lightroom and Photoshop. Lens profiles built into Lightroom and Camera RAW have the capability to completely eliminate it with a single click.

1.3) Mustache Distortion

The nastiest of the radial distortion types is mustache distortion, which I sometimes call “wavy” distortion. It is basically a combination of the barrel distortion and pincushion distortion. Straight lines appear curved inwards towards the center of the frame, then curve outwards at the extreme corners, as shown below:

Wavy Moustache Distortion

This is the reason why mustache distortion is often referred to as “complex” distortion, because its characteristics are indeed complex and can be quite painful to deal with. While this type of distortion can be potentially fixed, it often requires specialized software. You cannot just use the built-in tools in Lightroom and Photoshop, unless a specific lens profile is already built to combat such distortion. If you attempt to deal with such distortion as barrel-type, you will end up curving the extreme corners a lot more. And if you attempt to compensate for pincushion distortion, you will end up curving it for even stronger barrel distortion towards the center.

A number of older lenses, as well as some modern lenses have mustache distortion. A good example of this is the Nikon 18-35mm f/3.5-4.5D lens, which shows a rather nasty case of a mustache distortion.

2) Rectilinear vs Curvilinear Lenses

Some lenses are optically designed to be “rectilinear” (like the Nikon 14mm f/2.8D and the Canon EF 14mm f/2.8L II USM), where they yield straight lines without bending them (resembling human vision), while other lenses like “fisheye” lenses are designed to be “curvilinear”. Rectilinear lenses generally stretch objects to make them appear straight, especially towards the edges of the frame. Curvilinear lenses, on the other hand, do not stretch anything, but they heavily distort images by curving straight lines (like in door peepholes). Take a look at the following image samples that show both rectilinear and curvilinear lens effects:

Curvilinear vs Rectilinear Lens

As you can see, the fence on the curvilinear lens sample appears unnaturally curved – that’s because I photographed it using a fisheye (curvilinear) lens. The image on the right is what you would see from a rectilinear lens – the fence looks straight and natural, just like you would see it with your eyes. The size of the fence appearing large in the front of the frame and getting smaller at longer distances is perspective distortion (see below), which has nothing to do with optical distortion.

Rectilinear and curvilinear lens verbiage is typically applied only to wide angle lenses.

3) Perspective Distortion

So far we have been only talking about optical distortions. Another distortion type that is often seen in images is perspective distortion. Unlike optical distortion, it has nothing to do with lens optics and thus, it is not a lens error. When projecting three dimensional space into a two dimensional image, if the subject is too close to the camera, it can appear disproportionately large or distorted when compared to the objects in the background. This is a very normal occurrence and something you can easily see with your own eyes. If you take a smaller object like your mobile phone, then bring it very close to your eyes, it will appear large relative to say your big screen TV in the background (and the farther your phone is from your TV, the smaller the TV will appear relative to your phone). The same thing can happen when photographing any subject, including people.

For example, if you photograph a person with an ultra wide angle lens up close, their nose, eyes and lips can appear unrealistically large, while their ears can look extremely small or even completely disappear from the image. Take a look at the following photo of my son Ozzy, who I photographed with the Nikon 24-70mm f/2.8G lens at 27mm:

Impact Light Shed with Ozzy

Look at the size of his head – it appears disproportionately large relative to his body. His eyes, nose and lips are very much enlarged, while his ears are dwarfed. And this was only at 27mm! You can imagine what it would look like if I got closer to his face or used a wider lens at a shorter distance.

This is the part that seems to confuse a lot of photographers – the relationship (or lack thereof) of focal length to perspective distortion. You might hear some photographers say that one should use longer focal lengths to photograph people, or they will get distorted due to the lens’ short focal length. This is a mostly false statement, because lenses have no perspective. Other than fisheye lenses, all lenses have the same perspective – it is the camera to subject distance that determines perspective, not the focal length. There is an illusion of different perspective of lenses, because with long focal lengths you have to stand further away from the subject to frame them the same way. If you were to stand at the same distance, the subject would appear exactly the same! So if you take a 50mm lens and an 85mm lens, there is no difference in perspective between the two, as long as you stand in the same spot and keep the subject to camera distance the same. Yes, the subject would certainly appear smaller with the 50mm lens due to shorter focal length / wider field of view, but the perspective and proportions would be the same on both. So the point of longer focal length lenses in such cases, is the possibility to enlarge the subject in the frame, while keeping normal perspective. Telephoto lenses do not magically fix perspective distortion – they force you to move back from the subject, which is what changes the perspective.

Take a look at the following photograph of a red car:

Red Car Perspective Distortion

The car looks completely distorted, because I stood very close to it and photographed it with a wide-angle lens (Nikon 14-24mm). Note that the left part of the car looks disproportionately big – even the left light looks about 50% bigger than the one on the right, although you know that they are both the same in size. The car is occupying the majority of the frame and everything in the background looks relatively small. If I used a normal lens and stood in the same spot, I would have ended up with only a part of the car filling the whole frame. Yet, if I were to crop both images for the same field of view by heavily cropping the wide angle shot, the perspective distortion effect would be the same on both.

Here is another example of perspective distortion:

San Francisco Downtown

In this image of a downtown San Francisco street, the four story buildings to the left and the right look larger than the 48 story Transamerica Pyramid (the long building in the distance), when in fact they are much smaller if you were to put them side by side. Because I used a wide angle lens, I was able to show the front buildings much bigger than they really are.

The above examples of perspective distortion are known as “wide-angle”, or “extension” distortion. There is another kind of perspective distortion, which is the opposite of wide-angle distortion – it is called “telephoto” or “compression” distortion. Compression distortion is only possible with telephoto lenses, because it requires the photographer to stay at a long distance relative to the subject, which essentially makes very distant objects appear larger than they are when compared to “normal” perspective.

Lastly, there is also the case of converging lines. When the camera sensor is not perfectly parallel to the photographed object such as a building, it produces an image that at first might seem unnatural, due to its “leaning” effect, as shown below:

Legion of Honor

However, this is a perfectly natural perspective with no distortion, because your eyes would see this exactly the same way. Lens manufacturers offer “perspective control” or “tilt-shift” lenses to deal with this particular situation, but the result actually turns out unnatural, since that’s not how it looks in real life when we look up. Take a look at the below examples of before (left) and after (right) perspective control change:

Perspective Control

The image on the left is how you would see it with your eyes if you stood there, while the image on the right is what a perspective control / tilt-shift lens would do to the image, after it is aligned to the building.

Here are a couple of more examples of converging lines, where one part of the image appears much larger than the other simply because it is closer:

Golden Gate Bridge

Fences

Again, none of these are a result of distortion – that’s a natural perspective!

And lastly, one more example of perspective distortion involving people:

Inflating Balloons

Note how the balloons in the center of the frame appear natural, while the heads of the groom and the best man look egg-shaped. This is a direct result of using an ultra-wide angle lens at a very close distance and badly placing the subjects. If both sat back to back and inflated balloons in the opposite directions, their heads would have looked pretty normal being in the center, while the balloons would have been egg-shaped.

I hope this article clarifies differences between the different types of distortions. If you have any questions or comments, please let me know in the comments section below!

Comments

  1. 1
    ) Smudger
    August 13, 2013 at 4:15 am

    Strictly, perspective is simply spatial the relationship between objects and the view point.

    Lenses may render unusual images beacause of the angle of view, projection and optical distortions but they do not alter perspective.

    • August 13, 2013 at 7:22 am

      Smudger,

      you are completely right in saying lenses do not actually alter perspective, of course. But they do change how perspective is recorded in a photograph, how it is emphasized (wide-angle lens) or de-emphasized (telephoto lens) when compared to our vision.

    • August 13, 2013 at 1:52 pm

      Yup, exactly my point. Thank you for clarifying it further Smudger!

  2. 2
    ) Abhijeet
    August 13, 2013 at 4:19 am

    Excellent information, Nasim.

    I own the Sigma 150-500mm f/5.6-6.3 lens and although I have not faced any apparent distortion issues, is there anyway for users to actually determine if their lens (any lens) causes any or all of these distortions?

    Thanks,
    Cheers,
    Abhijeet

    • August 13, 2013 at 1:53 pm

      Abhijeet, do not worry about distortion on telephoto lenses – you will see a little bit of pincushion, but it is usually not a big deal. Plus, it is not like you will be photographing architecture with straight lines at 500mm :)

  3. August 13, 2013 at 8:29 am

    Fantastic post Romanas. If your readers are curious as to the “best”, IMO ultra-wide FX lens that I have found, I have been shooting with the Nikon 14-24mm for a few years now and just purchased a Sigma 12-24mm. While its only a 4.5-5.6, the lack of distortion is amazing, especially compared to the Nikon 14-24. The size and weight savings is substantial as well. Have a look at my website for a few examples of building shot with it in Chicago. No distortion corrections have been made in post.

    -Chad

    • August 13, 2013 at 8:32 am

      All of the images under Commercial were shot with the Sigma 12-24mm. At 24mm it even makes a decent portrait lens. Yes there is some distortion, buy my point being MUCH less than the $1000 more expensive Nikon. And yes. She is near TACK sharp. I would give the node to the Nikon for sharpness. But not by much. Very pleased indeed.
      Chad

  4. August 13, 2013 at 10:42 am

    Hi Nasim.
    A very interesting article which has opened my eyes about several concepts. For example the fact that wide angle lens are not the best for portraits. I was always trying to change my kit lens for a prime lens to make portraits, but its right that the most important is the distance to the subject.
    Thanks a lot
    Cecilio

    • August 13, 2013 at 1:23 pm

      Definitely Cecilio

      My favorite portrait lenses are the 85mm 1.4, 105mm, and 70-200 2.8. The 85 wide open at 8 feet is amazing with excellent bokeh. IF you are careful a 50mm lens will work but keep back at least 10 feet I find is best. Same goes for a 35mm back 12 feet.

    • August 13, 2013 at 1:56 pm

      Cecilio, yes, wide angle lenses can create a lot of distortion if you are not careful :)

      My favorite portrait lens is an 85mm, since it is not too short or too long for the right perspective. Nikon’s f/1.4 and f/1.8 are both phenomenal.

  5. August 13, 2013 at 2:39 pm

    Just a note Nasim, how useful and current your blog is. It is most impressive how active and attentive you are to it. Amazing. It is now the only blog I frequent on a regular basis to read the posts and comments.
    Thank you for the service!

    Chad

  6. 12
    ) Frank Jr.
    August 13, 2013 at 3:30 pm

    Fishermen have used Perspective Distortion for many years even before digital cameras were thought of.
    They would hold their catch far out in front of them closer to the camera making their fish appear bigger. Of course I never did that. (lol) ;-)

  7. 13
    ) Randall
    August 14, 2013 at 6:30 pm

    Funny that you wrote this article. I just took a trip with only the 18-35mm and I am noticing some shots have perspective distortion that I didnt notice when taking the photos. Good thing to remember when composing shots.

  8. 14
    ) uma
    August 17, 2013 at 4:58 am

    I never thought about perspective distortion while taking closeups. I have canon 18-55mm, 55-250mm and 100-300mm lens. which of these is best for portaiats and birthday shots. thaks for the very very useful information
    uma

    • August 26, 2013 at 1:13 pm

      Uma, don’t use the 18-55mm at 18mm and very close distances – that’s what will result in a lot of perspective distortion :)

  9. August 19, 2013 at 11:24 pm

    Just wanted to say thank you. I have been following Photography Life for a while now and you people have inspired and informed me about the nitty gritty of photography. The articles are of great detail and knowledge for beginners like me. Thank you Nasim and team.

  10. 21
    ) Chris Zeller
    August 27, 2013 at 10:27 am

    Great article again Nasim! I folow your blog daily and am constantly impressed. While this is all familiar territory, the diagrams are very well done and the explanations are clear.

    This is the #1 issue I am struggling with and I hope you will pick up the subject where you left off in a follow-up article discussing wide-angle composition. I am addicted to wide-angle perspective and how it can bring the viewer into the frame. I shoot the 14-24mm often. For inanimate subjects it works well like your car or golden gate bridge which are excellent images despite the distortion. But often my subjects are people (family photos) and the end up looking like your baloon blowers. How do you deal with “rule of thirds” composition with wide angle perspective of people. Placing the person in the center is certain to be boring. I’d love to hear what you do in these situations. Thanks as always!

    • October 2, 2013 at 11:49 am

      Chris, I try not to photograph people at all with super wide angle lenses, as the effect will make them look funny. If I do have to photograph with a wide angle, I will place the subject in the middle of the frame, where distortion is not present. With wide-angle lenses, it is best to put the subject as close as possible, to create a fun perspective, similar to the picture of my son in the above article. Don’t put people in the corners – that’s almost impossible to fix!

  11. 22
    ) Steve
    September 6, 2013 at 9:19 pm

    Hi Nassim, nice article.
    Would you say that Nikon lenses have slightly more distortion than Canon lenses, (generally speaking)?

    • October 2, 2013 at 11:47 am

      Steve, no, not really – both Canon and Nikon exhibit distortion on most lenses. That’s the nature of optical design!

  12. 23
    ) Hussein Aliyu
    September 18, 2013 at 2:32 am

    Thanks a lot. Very educative article on lens distortion. It probably explains why i sometimes don,t feel satisfied when i view an image I took compared with my expectations. I will henceforth utilize distortion correction in Lighroom.

    • October 2, 2013 at 11:49 am

      Thank you for your feedback! Distortion correction won’t fix severely distorted subjects though, as in the last image of this article – keep that in mind…

  13. 24
    ) BT
    October 1, 2013 at 4:23 am

    Very good article, I was wondering what knowledge you would have about publishers opinion on the subject. years ago I spoke to a published photographer about my landscape/ architectural work and he told me that I needed to invest in a tilt shift lens as “publishers don’t accept distorted images” similar to mine.

    • October 2, 2013 at 11:53 am

      BT, for landscapes and architecture, I would not be surprised if the publisher requires the fixed perspective. Not always natural, especially for architecture when you stand close to it (like a tall building when looking up), but what can you do if they want to see it straight? The only answer is a tilt/shift lens. In some situations, even a tilt/shift lens might not cut it and you might need to use a more flexible setup with bellows…a number of landscape and macro photographers rely on those for their photography needs.

  14. March 22, 2014 at 11:07 pm

    Wonderful article on distortion. The kind of explaination is good for all level of photographers. Thank you so much for your efforts.

  15. 30
    ) ghaziat
    March 23, 2014 at 7:23 pm

    I’m very confusing and thinking a lot to buy a lense thats good for low light filming and wide angle (rectilinear). Actually, I have limited budget not exceeding $900, and I need your help to guide me which lense is good for me. Also I want to use it for photography as well. I will appreciate your help by listing me the good lenses that satisfy my goal, thanks a lot.

  16. 31
    ) mona
    April 9, 2014 at 11:10 pm

    Respected Sir,
    How do i find the radial Distortion Coefficient?
    example:
    Camera Model: Canon A640
    Identification Tag: 4726208879
    Resolution: 480×640
    Focal Length: 660.8799
    k1: -0.18533
    k2: 0.21517

    k1 and k2 are distortion parameter.. i to find this for my camera lens

  17. 32
    ) xylosx
    April 30, 2014 at 1:10 am

    Excellent post! Really helped me understand the different distortions and perspectives with lenses! Thanks a lot!

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