Vignetting, sometimes known as "light fall-off", is basically the reduction of the saturation or brightness of an image at the edges relative to the central area. It arises as a consequence of artifacts that darken the edges of an image. The effect can be caused simply by using a lens hood that is too long for the focal length of the lens and which consequently obstructs the field of view at the margins. It can also be caused by other situations such as:
- the use of a lens designed for a smaller image format than that of the camera being used;
- using zoom lenses, particularly those featuring a large zoom range and used at their wide-angle limits;
- using any lens at its maximum aperture; or
- using a teleconverter or extension tubes to change the effective focal length of a lens.