read out noise (CCD)

The output signal of CCD sensors and CMOS sensors is affected by dark noise, which is the noise of the dark current, and the thermal noise of the readout amplifier and shows up in the readout noise of digital cameras.

Dark noise occurs when no light falls on the image sensors and the luminous flux generated corresponds to the dark current, which is superimposed with minimal noise. The sensor signals generated in this way are amplified in the readout amplifier, which adds its noise component to the dark noise.

The readout noise can be taken from the manufacturer's documentation of the camera manufacturers and is a dimensionless effective value determined from the number of electrons. For identification purposes, a small "e" is written behind the value, which stands for electrons. The readout noise lies between 10e and 100e.