Dark current
From The Glossary of Digital Photography
Current from a sensor when the camera is on but no light is hitting the sensor. Dark current causes dark noise. The dark current is the rate that electrons flow from the image sensor. Hot pixels are the bright spots in a dark image. These hot pixels are caused by the dark current noise. The higher the ISO, the longer the exposure, and the hotter the CCD becomes, the worse the problem and the more noticeable the hot pixels. This can be reduced by cooling the image sensor. Using a technique called dark noise subtraction can eliminate it. See also dark noise; dark noise subtraction
