3D-DNR: Digital Noise Reduction decreases picture noise and reduces colour mixture errors
3D-DNR stands for multidimensional digital noise reduction (DNR: Digital Noise Reduction) and was developed for shooting at night or in dimly lit places. On the one hand, 3D-DNR reduces unwanted picture noise, on the other hand the feature compensates for image distortion due to colour blending errors by extrapolating and removing even the smallest defective pixels.
One of the frequent causes of noise is the so-called dark current. This refers to the formation and excitation of electrons due to the heating of the recording sensor by the operating temperature and basic voltage of the camera. A certain level of ground noise is always present, but it is not noticeable in daylight operation. The reason for this is that intensity of the light that influences the photodiodes when it is bright and excites the electrons considerably more than the working temperature and device voltage.
The behaviour is different at dusk and when shooting at night: more electrons are now excited by heat and voltage than by incident light. The video signal and noise mix, and image distortion is the result.