# What is dark noise?

##### THIS GUIDE IS FOR:

Persons who are interested in noise

##### THIS GUIDE OFFERS:

A quick review of dark noise

Dark noise is statistical variation in the number of electrons thermally generated within the pixel in a photon-independent fashion, and is the electron equivalent of photon shot noise. Dark noise is calculated from the dark current:

$Dark\ noise=\sqrt{\mathstrut (dark\ curent\ [electron / time])(integration\ time\ [time])}$

Dark noise is statistical variation, so it cannot be avoided by applying background subtraction. The background subtraction is applied to remove the average of dark electron, that is, “dark current”.

Dark current, and therefore dark noise, are temperature dependent, with less noise at lower temperatures. For most biological experiments, dark current and dark noise are negligible over a typical exposure interval of less than five minutes.

Because dark noise is typically negligible, the main noise component coming from the camera that needs to be considered is read noise.