Noise is the digital equivalent of grain in film. It’s random electrical signals captured by the photosites on the camera sensor, and usually this background noise level is so low compared to the brightness of the captured picture itself that you just don’t notice it. But if you start increasing the camera’s ISO setting, the […]
Signal to noise ratio
All sensors capture a small base level of random digital noise, and the electrical circuitry around them can introduce noise too. The key technical measurement is the signal to noise ratio. The higher the ratio between the signal (the image you're capturing) and the random background noise, the better.