Anyone who owns a digital camera, or anyone who reads the camera reviews here on TrustedReviews, will be familiar with the concept of image noise, that grainy distortion that spoils pictures shot in low light conditions with high ISO settings. But what is image noise? Where does it come from, and what can be done to prevent it?
All electronic devices generate noise. The background hiss of a radio, the distorted sound of an over-amplified electric guitar, or the snow of interference on a badly-tuned television, all of these things are electronic noise, and so is the image noise in a digital photograph. All electronic signals contain of a certain level of noise as a background to the actual useful information being generated or transmitted. The relative level of information and background noise is called the ‘signal to noise ratio'.
In digital cameras this noise can come from a variety of sources. Some of it is internal noise generated by imperfections in the electronic components of which the camera is made, or simply as a by-product of their normal operation. For instance, capacitors generate a small amount of signal noise as they charge and discharge. Electronic components can also be affected by environmental noise, such as the electrical fields and electromagnetic radiation that constantly surround us.
Circuit noise can be minimised by efficient circuit design, superior manufacturing techniques and rigorous quality control. Unfortunately some cheaper camera brands, or even budget camera ranges from better-known brands, may use components that are built down to a price rather than up to a standard, which is why these types of camera generally produce noisier images than more expensive models.