vignettering

Vignettering is the gradual darkening or desaturation of an image toward its edges relative to the center. The effect is most noticeable with wide-angle lenses, fast apertures, or when light is partially blocked by the camera hardware or filters.

Causes of vignettering can be grouped into natural/optical, mechanical, and digital factors. Natural vignetting follows the cosine fourth power law: light rays striking the sensor at steep angles deliver less illumination, an effect that strengthens with wide fields of view and large apertures and diminishes when stopping down. Optical vignetting arises from lens design and element placement, causing uneven light transmission toward the edges even without obstructions. Mechanical vignetting occurs when parts of the camera system—such as the lens barrel, hoods, or filter stacks—partially obstruct light to the sensor. Digital or processing-related vignetting can result from uneven flat-field correction or aggressive post-processing.

Effects and usage: vignetting reduces brightness toward the image margins and can introduce color shifts if the channels are affected differently. In some contexts it is undesirable and corrected, while in others it is used intentionally to draw attention to the scene center or to create a vintage or cinematic look.

Measurement and correction: vignetting is often expressed in stops or EV of brightness falloff from center to edge. It can be corrected with lens profiles or flat-field calibration in post-processing, or by using appropriate equipment and technique to minimize edge obstruction. Prevention strategies include selecting lenses with better edge transmission, avoiding stacked filters, and stopping down when practical.