The two common forms of lens distortion are barrel distortion and pincushion distortion. These two complications usually occur when low quality or practical lenses are used. Wide range zoom lenses and wide angle lenses are notorious for causing lens distortion.
Both of these forms of lens distortion are likely to occur when using any of these lenses, but do you know the difference between the two lenses? Barrel distortion occurs when lines within the image bend outwards, like the lines of a building or trees. Barrel distortion causes an image to look as though it is wrapped around a spear. It causes the distance from the optical axis to decrease magnification. Pincushion distortion is the opposite. It occurs when the lines of the image bend inwards. This increases the magnification distance from the optical axis. It causes the image to be bowed inwards. Lens distortion causes an image to loose perspective because of the convex curves it causes in the images.
Complications of Lens Distortion
Barrel distortion and pincushion distortion present complications within images because people can easily spot geometric distortion when looking at an image. Lenses distortion is a quick way to ruin the quality of a picture. Barrel distortion is often easier to spot because the worst area of distortion is often the center of the image. It is again opposite for pincushion distortion, where the outer edges of the image are the most noticeable.
Avoiding Lens Distortion
There are many things you can do to try and eliminate the chances of any form of lens distortion from occurring. The easiest and simplest way you can avoid lens distortion is to not use the lens completely extended to its limit, or completely contracted to its limit.
Fixing Lens Distortion
If you end up with a distorted picture, all hope is not lost. Often, you can fix a distorted image with computer software. There are many programs available that will allow you to fix the distorted images easily. It may take some experimentation to correctly fix the image, but the extra time is worth it. The best way to fix lens distortion is to use one of these programs. Never crop an image. It may look fixed, but it will still have the distortion.
“Lens Distortion” DXO Optics Pro
“Barrel Distortion” By Vincent Bockaert Dpreview.com