Dark frame
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A dark frame is a photography technique to identify noise in a CCD imaging device. This is done by recording without exposing the CCD, usually by leaving the shutter closed and putting the CCD in a dark room. These "dark frames" are then subtracted from subsequent images to correct for extraneous noise in the CCD. The noise is often caused by hot pixels. Hot pixels are sensors on the CCD with higher than normal charge leakage. On long exposure, they can appear as bright pixels.
Sensors on the CCD that always appears as brighter pixels are called stuck pixels while sensors that only brighten up after long exposure, are called hot pixels.
The dark frame technique is also used in digital photogrammetry, e.g. to improve the contrast of satellite and air photograms.
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