(1) Extraneous, unwanted signals that invade an electrical or optical system. In electronics, noise can come from strong electrical or magnetic signals in nearby lines, from poorly fitting electrical contacts and from power line spikes. In optics, noise comes from the stray reflections of light that emanate from the various components in the optical system. See signal-to-noise ratio and noise cancellation.

(2) Distortions in analog and digital video images that are caused by a variety of circumstances. The silver grains in the original film create granular noise. Electronic circuits create Gaussian noise. Drop outs and bit errors in digital tapes create impulse noise, and the digitization process creates quantization noise. See Gaussian noise, dynamic noise reduction and artifact.

(3) Distortions in a still image caused by variations in the pixels in the CCD or CMOS sensor. See digital camera.