When a picture is taken with a traditional camera lens, the picture’s center appears brighter than its edges. This effect is more pronounced with wide angle lenses and long telephotos and is known as vignetting or light fall-off. Vignetting can occur by accident, which negatively impacts a photograph’s quality or the photographer may purposely do it to achieve a desired effect.

Why does Vignetting Matter?

When a minor or major fall-off in light results from the vignetting effect, it dramatically impacts the way people perceive the picture. The photographer’s original vision or intention for how he/she wanted to convey information is done less efficiently and the desired emotional response from the image is also affected. Some photographers, however, purposely use the vignetting effect in order to keep the viewer’s eyes within the picture’s frame.

How Vignetting Impacts an Image

The most noticeable effect that vignetting has on a picture is the gradual darkening towards the corner edges of the image. When the picture’s focus has a large zone with even brightness or color, the effect is more noticeable. The vignetting effect significantly darkens pictures of a large number of people or of architectural structures. When cropping a picture that vignetting has impacted in a non-symmetrical way, the picture is negatively impacted unless special care is taken to account for the darkening effect’s radial symmetry.

How Hard is it to Correct Vignetting?

There are a number of factors that have to be accounted for when attempting to correct vignetting. First, the effect increases as the lens’s focal length increases and is worse with zoom lenses. Next, for lens assemblies that have a wide aperture, the lens body on the edge of the field of view shields the entrance pupil, resulting in a vignetting increase with aperture. Other factors that have to be accounted for are tone curve dependency and over-exposure risk (with significant areas of bright or darkness). The appearance of increased noise levels for darker pictures must be avoided. The best results for vignetting correction occur on an image-by-image basis and can be time or labor intensive.