Perspective correction is a procedure for editing photographs to better conform with the laws of perspective. Assuming that the view direction of the photographer was parallel to the land surface when the photo was made, the correction would:

• make all lines, which are vertical in reality, vertical on the image. This includes columns, vertical edges of walls, lampposts
• make all parallel lines (such as four horisontal edges of a cubic room) cross in one point

Perspective projection distortion occurs in many photographs, especially when they are taken from above or below the photographed object.

Compare the two images to the right. The first suffers from perspective distortion - in the second that distortion has been corrected.

The popularity of amateur photography has made distorted photos made with cheap cameras so familiar that many people do not immediately realise the distortion.

In the past professional photographers corrected the photos during printing by placing the film at an angle to the photo paper. Today professional cameras sometimes have lenses that can correct the perspective during filming by rotating relative to the exposure area of the film.

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• illustrations (NB: Text is in Russian)