@Larry Kurfis well good luck dialing in a correct exposure without adjusting ISO in darker situations. You don’t seems to want to understand what I’m saying, what was the purpose of the question? To get people to understand exposure and how to use this parameters in the best way to be able to photograph or to confuse everyone who tries to understand the important aspects of exposure. Even if ISO doesn’t let more or less fotons in to the sensor as shutter speed and aperture does you can’t cut ISO out of the equation when you set your camera up for photography. It’s as simple as that, and a you don’t need to complicate it more than that. I know exactly what you or chat gpt are talking about. If you adjust one of this tree parameters one stop you need to adjust one of the other parameters (S, A or ISO) one stop to get the same exposure, except if you use a one stop strong ND filter to adjust the amount of light allowed in to the sensor.