Interesting article that will show you how to correct the barrel distortion caused by many of today’s digital camera lenses. (Now, if you paid 2K for that sweet Canon 85mm, f1.2… and you are still getting barrel distortion… well, you shouldn’t be getting any distortion at all.) The settings that you create with this article will allow you to repair all images made on that lens with the same settings. Cool.
“The following examples demonstrate the use of my Photoshop/Gimp plug-in Panorama Tools to correct lens distortions. The most common and annoying lens error is barrel distortion, which occurs in many cheap wide angle lenses, especially in digital cameras or when using wide angle adapters. Straight lines are bent away from the center of the image: A rectangle looks like a barrel. Correction of these distortions is performed by shifting each pixel radially. The displacement is calculated using a polynomial function, whose coefficients are specific to the particular lens. Once these coefficients have been determined, they can be reused for each image: In practice the images should be batch-converted to correct these errors. Panorama Tools employs a high-quality sampling algorithm with negligible image degradation, so no new errors are introduced during this process.”