Barrel and Perspective Distortion
The following image, a photograph of the Standard Insurance Center, was taken with a wide-angle lens. The camera was tilted up to include the facade. This caused vertical features to converge near the top and is an example of perspective distortion. Also notice that the horizontal features, that are actually straight, appear to be curved in the image. This is an example of barrel distortion. Choose the radio buttons below to correct barrel distortion, perspective distortion, and view the final image.
Vignetting, or a slight darkening of the edges and corners of an image, can occur with some wide-angle lenses. You can compensate for vignetting, and lighten the edges and corners, using the controls in the Vignetting tab. For the following image, a homemade loaf of pain à l'ancienne (old-fashioned bread), the Vignetting sliders are reversed to darken the corners for dramatic effect.
The following image has a severe case of chromatic aberration (CA). Click on the 100% crop to view the color fringe that surrounds contrasting features. CA is often most severe near the corners of an image and decreases in effect towards the center. PTLens enlarges or shrinks individual color channels to compensate for this effect. The net result is a sharper image. The change is difficult to see in the small image shown below, but is obvious in an 8"x10" print.
Fisheye images are distinguished by immense amounts of barrel distortion. Special facilities exist in PTLens for converting fisheye images to rectilinear images. In this case no calibration is necessary as sliders are provided for maximum flexibility.