picture noise
Image noise refers to the disturbing image particles in digital photos that reduce the quality of the image. Image noise is caused by the inherent noise of electronic components and circuits such as the image sensor and the image intensifier. In terms of effect, it is comparable to film grain in classical photography.
Image noise occurs wherever images are digitally recorded, converted, amplified and processed using a digital camera, camcorder, scanner or film scanner. For the viewer, noise is a disturbing effect that accumulates in the various electronic components and is evaluated by the ratio between the useful signal and the disturbing signal, the signal-to-noise ratio (S/N). Above a certain magnitude, the image noise is no longer perceived as disturbing. This size is at a signal-to-noise ratio of greater than 25.
Image noise is the accumulation of brightness noise and color noise, shot noise and amplifier noise. Like any other noise, image noise is caused by level fluctuations. It is particularly pronounced with dark images and high light sensitivity, because the individual CMOS or CCD sensors have different sensitivities and because, in addition, the amplifier downstream of the image sensor must be controlled more strongly with dark images. Furthermore, the noise depends on the pixel size of the CCD elements. The larger these are, the lower the brightness noise, and the greater the light sensitivity, the greater the image noise. On the other hand, this means that CCD or CMOS sensors with many small pixels close together have higher image noise than digital cameras with low resolution.
The easiest way to fix the problem of image noise is with a larger image sensor with larger pixels, or with fewer pixels on the same sensor area. Such a sensor receives more light per pixel, producing more photons and a stronger signal that is better amplified and less affected by thermal noise.