The most common distortion encountered in photographs is lens-barrel distortion that is readily apparent when using wide angle or fish-eye lenses. In some cases, distortion may be sought after in the picture to create a unique image, but photos that need to be accurate should have the barrel distortion corrected. You can alter the picture before it is shot by using a “Tilt and Shift” lens on your camera, or you can correct the image in postproduction using a photo-editing program.
Connect your camera or memory card to your computer using a USB cable or card reader and download the images to your hard drive.
Open the photo-editing program of your choice.
Open the image you want to adjust by clicking on “File” in the navigation bar, then “Open” locate the image you just downloaded and click “OK” in the bottom right of the window.
Click on “Image” then “Transform” then “Perspective” if you are using Photoshop; in Gimp and Paint.net, click on the “Perspective Tool” in the left margin of the program's main window. You also can hold the “Shift” key and press “P” to select the tool.
Click and hold the bounding box handles and stretch them outward to adjust the image until the proper perspective is achieved.
Click on “File” then “Save As” to save your adjusted image.