Ralph III wrote in post #13591141
I want to know exactly HOW a digital camera's "sensor" can/is changed with different ISO settings?
To my knowledge the sensor itself is unchanged by increasing the ISO setting on the camera. Only the electronic "gain" of the "computer" is changed. Unfortunately, usually when you change the gain, you change the signal to noise ratio. At a low ISO setting, the signal is greater than noise (hopefully) in this ratio. At a higher ISO setting, the amount of noise in ratio to signal is increased, thereby giving you more noise (digital grain) in your image.
If you were to set your ISO on automatic (as some EOS cameras provide), the ISO will self adjust to help you meet the aperture/shutter speed/ISO triad as you describe above when you day, "...slow shutter setting and wide open Aperture, is a request for more light?" But then you have ceded that control to your camera and risk introduction of unwanted noise.
As I understand it, the sensor has a "native" ISO setting at which it has its best signal to noise ratio. This native ISO is not adjustable... it is what it is. When you move from that value, the data quality decreases due to the greater noise in your signal to noise ratio.
This is an over-simplistic explanation and therefore must contain inaccuracies.
Perhaps if you are more clear with your questions we can provide better help for you. A few of us have tried to explain this to you given the questions that you have asked.
If you desire more specific electrical engineering based explanations, perhaps someone will come along. Otherwise, I would suggest performing an internet search.