vignetting

Vignetting is the gradual reduction of image brightness toward the periphery compared with the center, often appearing as darker corners. It is a common optical effect in photography and cinematography and can affect color and contrast as well as luminance.

The causes of vignetting fall into optical, mechanical, and electronic categories. Optical vignetting results from the geometry of light as it travels through a lens system; the cosine-fourth law describes how light at steeper incident angles reaches the sensor, causing stronger falloff toward the edges, especially with wide-angle lenses and large apertures. Mechanical vignetting occurs when physical obstructions such as the lens barrel, filter rings, or lens hoods occlude peripheral light. Electronic or digital vignetting refers to brightness reductions arising from sensor characteristics, readout, or processing workflows that unevenly affect edge regions.

Vignetting is often more noticeable with wide-field lenses, at wide apertures, and on full-frame cameras, though it varies with lens design and sensor size. It typically diminishes with stopping down the aperture or using lenses designed to minimize edge shading. Proper filter installation, longer focal lengths, or avoiding obstructive accessories can also reduce mechanical vignetting.

Correction and mitigation are common in both photography and scientific imaging. Post-processing tools can apply a radial correction to restore uniform brightness, using either a calibration image such as a flat-field frame or a lens-specific vignetting profile. In scientific imaging, flat-field calibration is routinely used to remove vignetting from data, ensuring consistent illumination across the frame.

In practice, vignetting is a well-understood phenomenon and is often corrected or minimized, though it can be used creatively in some photographic and cinematic contexts.