Geometric Lens Distortion: a common problem in photography

Camera don’t always capture geometry as the eye perceives it, and DxO’s engineers have established means of correcting these distortions with efficiency and precision.

What is Lens Distortion and what causes it?

All lenses produce a certain amount of geometric lens distortion. This is caused by a range of factors, such as the curvature of the lens, the focal distance, and the angle at which the photo was taken. It affects the image in a variety of ways and is especially apparent when straight lines at the edges of the frame become curved.

Geometric lens distortions primarily occur when the focal distance is short (resulting in barrel distortion), long (pincushion distortion), when the photo is taken at an oblique angle (keystone distortion), or with a wide-angle lens.

Distortion can make straight lines in an image appear curved, especially toward the edges of the frame.

How does DxO correct lens distortions?

To measure the degree to which a lens produces geometric distortion, DxO’s experts use a combination of different focal lengths and distances. They photograph a reference image that features dots laid out on a very precise grid. Depending on the lens and camera combination being used, this process can require 100 to 500 reference images.

The extent of the distortion is then precisely calculated for each position in the field of view. With this series of measurements, an algorithm calculates an average and maximum level of distortion. These values are then arranged on a precise scale. Below 0.3%, the distortion is not perceptible to the untrained eye. Between 0.3% and 1.0%, it is visible. Any value above 1.0% is considered problematic.

The calibration data obtained by the analysis are compiled in a correction file called an Optics Module.

The degree of geometric distortion in a lens is evaluated using a reference image containing a dot plot laid out on a very precise grid.

Better lens distortion corrections than any other software

Correcting geometric lens distortions is much more than a matter of simply straightening lines. DxO’s algorithms even correct the most complex distortions, including the keystone effect. This occurs when a large subject is photographed from an oblique angle with a wide-angle lens.

To achieve even better results when correcting the geometric distortions that occur with wide-angle lenses, DxO algorithms also remove volume anamorphosis, which means objects located at the edge of the frame retain their original shape.

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DxO corrects every type of lens distortion with flawless precision.


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