Correcting Lens Distortion

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Correcting Lens Distortion

There are a few things you might want to address before you begin adjusting the color or contrast of your images. One of these things is lens distortion.

A camera's lens can produce distortion. This is particularly true of zoom lenses zoomed to their wide-angle and telephoto extremes and of ultra wide-angle lenses. With telephoto lenses you can get barrel distortion, which makes your image look like it's bowed around the edges. With wide-angle lenses, you can get pincushion distortion, which makes your image look like it's pushed in in the middle. And fisheye distortion, which you get with ultra wide-angle lenses, makes your image look as if it's being reflected on a sphere: Areas in the middle are enlarged while areas at the edges are compressed. Fortunately, all three kinds of distortion can be corrected with A djust > L ens Correction.

Figure 8.1 shows the dialog box for Barrel Distortion Correction.

Figure 8.1. Barrel Distortion Correction.

Note that although the Preserve central scale setting isn't very important for Barrel Distortion Correction or Pincushion Distortion Correction, it is very important for Fisheye Distortion Correction, because in fisheye distortion the difference in scale between the center of the image and the edges is extreme.

NOTE

CAUTION

Always correct lens distortion before you crop or rotate your photo. The Lens Correction commands make assumptions about your image that do not hold once the image is cropped or rotated .

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