Noisy recorded scenes can dramatically increase the size of the digital files (which are usually archived over time on a remote hard disk). In extreme cases, noisy scenes can reduce the archive period. For example, from a month of video to no more than a week! Electronic noise is caused by a number of sources, including cable attenuation, thermal effects, and over-amplification. The camera itself can also be a source of noise, which is seen as snow or graininess in the displayed image.
Some cameras include Dynamic Noise Reduction (DNR) to enhance image quality by reducing or canceling electronic noise, especially in low-light conditions. The DNR system in the Bosch DinionXF camera cancels out noise by comparing images produced over time. A powerful algorithm developed for the 15-bit DSP then performs a pixel-by-pixel audit of the pictures, and any small, random changes that are symptomatic of noise are automatically eliminated from the scene.
