There are a handful of lens distortion types cited in lens reviews, but the two most common are pincushion distortion and barrel distortion. Both types are classified as optical aberrations that make straight lines deform and appear to be curved. Let’s break ’em down.
Let’s use a grid to visualize how these two distortion types affect images. A perfect lens (which doesn’t really exist) would capture the grid like this:
Pincushion Lens Distortion
Pincushion distortion is when straight lines appear to form concavity in the center of the image. This is common in telephoto lenses (prime and zoom), but generally doesn’t show up in normal or wide angle lenses. It looks something like this:
Barrel Lens Distortion
Barrel distortion is just the opposite of pincushion distortion: straight lines are bulged out from the center as if convex. This is most commonly an aberration of wide angle lenses and looks something like this:
All-In-One Zoom Lenses: The Perfect Storm
You can find both pincushion and barrel distortion in zoom lenses that try to cover wide angles and telephoto, such as the AF-S DX NIKKOR 18-140mm f / 3.5-5.6G or the Canon EF-S 18-200mm f/3.5-5.6 IS. The more expensive pro or semi-pro dSLR lenses in this category offer some nice reductions in these distortions, but they will be present to some extent in almost any lens that has wide or telephoto angles of view (or both!).
Correcting Lens Distortion
Luckily for modern digital photographers, many options for distortion correction exist in software form. Photoshop and Lightroom both offer lens correction “profiles” for a stunning array of lenses. These profiles are easy to apply and offer some degree of tweakability to get straight lines as straight as possible without warping other areas of the image. And, the software identifies which lens was used by scanning the EXIF data in the image.