Correcting vignetting
with science

Nohcab

Snæfellsnes Peninsula, Berserkjahraun, Iceland

DJI Mavic 3

12.29-29.85mm f/2.8

ISO 100 - 1/50 - f/4.5 - 12mm

DxO PhotoLab

Resolving darker corners is more complex than simply adding some brightening.

DxO corrects an image based on scientific analysis — and without undermining quality.

Vignetting can be an artistic choice, but it’s not always desirable and can affect the quality of an image.

What is vignetting?

Vignetting describes the reduced exposure at the periphery of an image. It can occur for several different reasons and can be affected by the design of the lens as well as the focal length and aperture used to capture an image.

Natural vignetting occurs when light reaches the sensor at different angles. Consequently, it is commonly seen in wide-angle lenses.

Optical vignetting is more dependent on the design of the lens and is more common when photographing at a wide aperture.

Vignetting can be reduced by avoiding wide apertures, but that's not a practical solution. Correcting vignetting with DxO Modules allows you to shoot at any aperture, without any vignetting.

How is vignetting
corrected?

To correct vignetting, several factors are taken into account: brightness, exposure, and color alteration. A blanket approach to resolving vignetting would shift colors or lighten an entire image, including parts where it is not required.

DxO’s scientific approach

Modern lenses

Due to the complexity of modern lenses, and several types of vignetting adding up, the light falloff does not simply follow the cosine-fourth-power law that you might remember from your optics textbook. To accurately characterize the vignetting of a lens, the light falloff should be experimentally determined at each point in the field, and for each focal length, focus distance, and aperture.

DxO technicians

DxO's technicians create a map of the vignetting effect by photographing an evenly lit target. This is less trivial than it sounds: achieving homogeneous illumination on a surface of several square meters, as required for extremely wide-angle lenses, requires careful setup and perfect control over multiple light sources. For meaningful vignetting measurements, the illumination must not vary by more than 10% — much less than what our eye can perceive.

Measurements

The technicians then measure the light fall-off for each part of the frame. Each pixel is then allocated a value describing the amount of light it receives compared to the center of the frame. These values are then used to correct images pixel by pixel.

Based on the lens-camera combination being analyzed, up to 500 sample images are created in order to generate the data needed to make a vignetting map.

The calibration data obtained through this analysis are compiled into one single correction file — a DxO Module — for each corresponding lens and camera pairing.

How DxO
corrections go further

Once we know the light falloff coefficient in each point, correcting vignetting could be as simple as multiplying each pixel by the corresponding coefficient. However, it must be noted that vignetting can (accidentally) help to preserve details in the highlights, typically on clouds in the upper corners of the image. Amplifying these areas could lead to loss of detail and potentially introduce hue shifts.

This is why, while applying the correction, we adapt the calibrated model to each individual image and its particularities. Our correction removes vignetting but preserves every detail.

Jmagerie

France

Nikon Z9

200-400mm f/4

ISO 110 - 1/2500 - f/4 - 400mm

DxO PureRAW - DxO PhotoLab

DxO Modules
give photographers
the best possible results

Because of the meticulous analyses carried out in DxO’s exclusive laboratory, and because of the intelligent means by which this data is used, photographers can be sure that they’re getting the best from their cameras and lenses.