Lens distortion isn’t a topic surrounded by excitement but it is something to be aware of when choosing your equipment and composing images. Even if you’ve never heard of it, you’ll still probably recognize at least one type of lens distortion. Heck it’s even boasted as a feature in some lenses!
The most common and recognized lens distortion is called Barrel Distortion. Wikipedia defines barrel distortion thusly:
In barrel distortion, image magnification decreases with distance from the optical axis. The apparent effect is that of an image which has been mapped around a sphere (or barrel). Fisheye lenses, which take hemispherical views, utilize this type of distortion as a way to map an infinitely wide object plane into a finite image area. In a zoom lens barrel distortion appears in the middle of the lens’s focal length range and is worst at the wide-angle end of the range.
Barrel Distortion like this:
You might recognize it as “Fisheye” distortion. I have an 8mm Russian fisheye that has this distortion in droves. Most super wides do. Where it becomes important to you is in the medium-wide range, around 24-28mm on a 35mm camera. Cheap lenses will distort more. Case in point I took this with a fisheye adapter for my iPhone that cost $20 and included three lenses!
A lesser known type of lens distortion is called Pin Cushion Distortion. It’s pretty much the exact opposite of barrel distortion. Instead of lines bowing away from the center, the curve towards it. Wikipedia’s definition of pin cushion distortion is:
In pincushion distortion, image magnification increases with the distance from the optical axis. The visible effect is that lines that do not go through the centre of the image are bowed inwards, towards the centre of the image, like a pincushion.
Here’s what pin cushion distortion looks like:
Like barrel distortion this occurs more commonly in lower quality optics.
How does this effect composition? With both types of distortion the effect is least noticeable towards the center of the lens. Further the effect doesn’t effect the center X and Y axis of the lens.
So if you want to take a picture of the sunset on the ocean and you have a lens with barrel distorting, place the horizon line in the middle of the frame. This will keep it straight (supposing you don’t want it curved for effect).
Barrel distortion can also be used creatively in images.
When photographing people barrel distortion can make people look bigger, or rounder. Close up it can make a nose look huge while ears disappear.
On the other hand pin cushion can have a slimming effect on people.
Both cam be difficult with buildings as the straight lines will curve.
Testing your lens can be as simple as photographing a tile floor or brick wall. Anything with parallel and perpendicular lines should work. You’ll quickly see if you lens distorts and by how much. The more you understand how your equipment “sees” the more control over your image creation you’ll have.
There’s a third type of disortion called “mustache distortion.” Wikipedia says of mustache distortion:
A mixture of both types, sometimes referred to as mustache distortion (moustache distortion) or complex distortion, is less common but not rare. It starts out as barrel distortion close to the image center and gradually turns into pincushion distortion towards the image periphery, making horizontal lines in the top half of the frame look like a handlebar mustache.
I was surprised to hear about this type of distortion. Pin cushion and barrel are all that’s usually mentioned in books and the only ones I’ve encountered in the wild.
If anyone has any examples of mustache distortion, link them in the comments, I’d love to see them!
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