Hot Pixel
A photosite with abnormally high dark current that records as a bright coloured dot in long exposures.
Measured in
count
In depth
Hot pixels are present on every sensor and increase with age, temperature and exposure length. They appear at fixed locations, which makes them easy to remove automatically — cameras map known ones and raw converters detect the rest. They become obvious in astrophotography and any exposure beyond a few seconds.
Examples in practice
A thirty-second night exposure shows a scattering of red and green dots that a two-second exposure does not.