Understanding Barrel and Pincushion Distortion in Lenses

Are you about to buy a new lens? Do you know its barrel and pincushion distortion ratings? Huh? What's that?

Barrel and pincushion distortion are present—at various zoom settings—in most zoom lenses of any price; although, well controlled in the more expensive lenses. The worst distortion is often seen in wide to super-wide angle lenses. While not a terrible problem most of the time, these are forms of distortion that you should be aware of, especially is you plan on using a new lens for shooting architecture or any type of pictures with lots of straight lines.

What is Barrel and Pincushion distortion?

Imagine the way a barrel bulges outward in the middle with a narrow top and bottom and you can understand barrel distortion. Pincushion distortion is the opposite; the top and bottom are wide while the middle bows inward (figure 1). You won’t see these effects in a terribly pronounced way in most cases, unless the lens is a cheap, uncorrected lens.

Figure 1 – Examples of distortion: barrel (left) and pincushion (right)

Figure 1 shows two pictures I took of a door frame. I later greatly exaggerated the barrel and pincushion distortion in Photoshop® so I could show you the effect. If you find a normal lens with this much distortion I would dispose of it or use it for special effects only. Some fisheye super-wide lenses can approach these levels of distortion (figure 2).

Again, most zoom lenses will generally have these two distortion types in varying degrees and at different zoom settings. Most of today's new lenses are well corrected and have very low distortion amounts; therefore, it is usually not a big issue. Some lenses have a small amount of barrel distortion at wide settings and pincushion distortion at telephoto settings.

For most photographers who shoot nature, portraits, sports, friends, and family these aren’t overly important problems. Again, for a photographer who shoots architectural images, or for those having many straight lines in their images, this can be an important issue.

Figure 2 – Samples of super-wide lens barrel distortion

Wide-angle zoom settings tend to have more issues than longer lens settings. If you get close to flat or straight objects with a wide-angle lens you may notice that the subject tends to bulge towards you in a weird way. In figure 2 you can see clear barrel distortion when I shoved my super-wide lens up close to the faces of two of my unsuspecting former friends. Not quite flattering, huh?

On the other hand, you may experience the opposite effect with longer lens settings. You’ll need to experiment with your lenses to see if anything looks objectionable.  A good way to test for barrel or pincushion effects is by putting your camera on a tripod and shooting pictures of things like door or window frames.  If you see the edges curving out, that’s barrel distortion, curving in is pincushion distortion.

Again, read lens reviews before you buy a new lens and see if the distortion is bad at certain settings. Newer lenses are generally well corrected for these two concerns.

Keep on capturing time...
Darrell Young
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