Barrel distortion is a curving distortion that happens to vertical lines when using a wide angle lens.
Barrel distortion can be improved by using any photo editing program that has tools to correct camera lens distortions. Adobe Photoshop 7 was used to illustrate this tutorial, but other photo editing programs have similar tools. Check your software’s HELP menu as the tool may be located under a different menu, or called by another name.
How to improve barrel distortion
This tutorial illustrates the technique using the Perspective and Free Transform tools in Photoshop 7:
1. Select the Perspective Tool (Edit menu > Transform > Perspective). Once the Perspective Tool is selected, pull one of the upper handles to the right (or left).
Free Transform Tool
2. A subject tends to shorten when using the Perspective Tool so, next, use the Free Transform tool (Edit menu > Free Transform) to drag the middle of the photo upward. Some cropping of the image will occur.
It is important to make adjustments to barrel distortion on a full sized image since the image will have to be cropped. Only after the distortion is tweaked should an image be further edited such as adjusting brightness and contrast or sharpened.
Other programs that correct barrel distortions
Other photo editing programs include more sophisticated tools to correct barrel and other lens distortions such as PTLens. Photoshop CS and above have a Lens Correction filter.