Image sensors and optical devices

How does the size of shot noise, caused by statistical fluctuation in the number of photons, relate to the number of signal electrons N?

  1. AProportional to N
  2. BProportional to √N
  3. CConstant regardless of N
Show answer and explanation

Answer: B. Proportional to √N

Photons arrive randomly, so the number of signal electrons N fluctuates by about √N. This is shot noise, and the signal-to-noise ratio is N / √N = √N, so more light gives a better S/N. It is the fundamental reason noise is noticeable in dark scenes.

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