I am trying to get my head around this topic so I would appreciate comments on how I think it works.
1. If the mode is A. The camera will raise the ISO up to the maximum entered in the ISO sensitivity setting and if that will not allow for sufficient exposure the camera, as a last resort, reduce the Shutter speed below the # set as Minimum shutter speed.
2. If the mode is S. The camera will raise the ISO to the maximum ISO sensitivity BUT will not lower the shutter speed set. In this situation the image will be underexposed.
As a related question I shoot our grand children's hockey games. I need a fast shutter speed so I would think I should use mode S. However this may result in underexposed images. What if I used S and then enter minimum and maximum ISO that I am confident will not result in underexposure? This way I can ensure a fast shutter speed.
Thoughts and recommendations on the above would be appreciated.