Overcoming geometric
lens distortions

Few lenses capture the geometry of a scene with absolute precision — especially standard zooms and wide-angle lenses. The elements of a lens often introduce various distortions and while many of these are minor, others can be prominent and disruptive.

DxO’s engineers have established unique means of measuring and correcting these distortions so that they can be removed with a level of efficiency and precision that’s well beyond other software, and even the manufacturer’s own profiles used by your camera.

Distortion — like the ‘barrel’ effect shown here — makes straight lines in an image appear curved, especially toward the edges of the frame.

What is geometric distortion?

An ‘ideal’ lens would translate any straight lines in the scene into identically straight lines in the image — a situation called ‘perfect perspective projection.’ Unfortunately, that ideal doesn’t exist in real-world photography, and the deviations from it are classed as geometric distortions.

By combining several lenses, and by using aspherical elements, lens designers can minimize these aberrations, but there are trade-offs between the image quality and a lens’s cost, weight, zoom range, and so on. What’s more, it’s not unusual for lenses that go from wide to telephoto to demonstrate different types of distortion throughout their zoom range. Therefore you might see some barrel distortion at wide focal lengths, which then shifts to pincushion distortion at the longer ones.

Modern lenses with their many elements — and especially mirrorless lenses — can also exhibit more complex distortions than these three well-known types, and therefore characterizing the issue requires more elaborate models with many parameters.

The resulting data is compiled into the unique DxO Module for that lens/camera combination, allowing DxO software to correct an image.

It’s worth noting that when geometric corrections are applied and the image is warped to straighten lines, its edges will become curved and must be cropped to create a rectangle. The accuracy of DxO’s corrections — their ability to tackle higher-order distortion, and the fact that they cover more focal lengths and focus distances — allows us to keep the maximum available field of view compared to competitors’ more simplistic calculations.