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Can someone explain to me how ISO on a digital camera works? Are several pixels combined (the resolution lowered)? I always think it's odd to have ISO settings

• dietrichepp 12y ago
  No, the ISO setting adjusts the analog gain before conversion to digital. As you would expect, this raises the noise floor. It is natural and expected to be able to adjust speed on a digital camera, because the dynamic range of a ADC is limited, and you want to be able to use that range optimally. For example, suppose your camera has a dynamic range of 10 stops. If you are shooting a scene with a dynamic range of 8 stops, then you get +/-1 stop of latitude where mistakes in exposure can be corrected digitally. Overexpose, and the signal will sometimes be above the range of the ADC. Underexpose, and the signal will sometimes be below the range of the ADC. You can adjust either the exposure (aperture, shutter speed) or the signal gain (ISO) to get the signal into the right range. You do the same exact thing when you're recording digital audio: you adjust the gain so that you use most of the range of the DAC. As in photography, you can try increasing the gain afterwards, but you might get problems with noise.