A hot pixel or bright dot defect is a pixel that outputs many more electrons than others at the same input signal in a charge-coupled device (CCD) or CMOS sensor. In the simulated image, the hot pixels are the sources of the salt-and-pepper noise. In the definition of the HST ACS, A pixel above 0.14 eï/pixel/second is considered a "hot" pixel.
A warm pixel is a pixel that has negative bias values. In the definition of the Hubble Space Telescope, a pixel below the hot pixels range but above 0.06 eï/pixel/second is considered a "warm" pixel.