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In order to understand the technology in a digital camera, I considered the following question:
How does ISO setting change CCD/CMOS sensor behavior?
For example, does ISO setting affect the amount of charge that each photon generates in the sensor, or does it merely change the amplification of a fixed charge from each photon. High end cameras allow for ISO in the range from 100 to e.g. 51200, thus a factor from 1 to 512, so it appears that the electronics allows for a pretty large range. A reference to an article would be appreciated.