Vignetting

In photography and optics, vignetting is a reduction in image brightness in the image periphery compared to the image center.

Although vignetting is normally unintended and undesired, it is sometimes purposely introduced for creative effect, such as to draw attention to the center of the frame. A photographer may deliberately choose a lens which is known to produce vignetting. It can also be produced with the use of special filters or post-processing procedures.