Perspective distortion (photography)

Converging lines in photographs vertical lines and edges called who strive to a common point, although they are parallel in reality. The effect occurs when the vertical or vertical edges of the intended image object are not parallel with the screen.

Example of converging lines, from street level perspective with wide-angle lens

Correction of undesirable distortions

Equalized image with digital image processing ShiftN

A photographic camera is covered - like the human eye - the laws of central perspective. Parallel lines in the scene are therefore only then also run parallel to the picture when they are in the motif in a plane that is parallel to the film plane. So when the camera is rotated, for example in front of a house up, develop converging lines, the house seems to tilt backwards.

But sometimes there is a desire to eliminate such " distortions "; if the required action is called shifting. For large format cameras and the tilt and shift lens by small-and medium-format cameras, this is avoided by not swung the camera to compose the image, but the picture detail.

Before the " equalization " of an image should be checked whether the respective unprocessed original was suitable or too contrary to the normal viewing habits after processing the result from the viewer. If unsuitable recordings equalized with converging lines by working with the appropriate software, the photographed object can be greatly distorted. These arrangements, which represent vertical lines under all circumstances parallel, then you can look unnatural, because they no longer correspond to the viewing habits of people (especially cuboid or cylindrical objects seem to diverge upward to get bigger ). Can avoid this effect often by correcting the vertical lines only moderate, ie not to the point of concurrency.

Examples:

After equalization plus post

Shot with 17mm shift lens

Shot with 17mm shift lens from another shooting direction