Just got the 6D and love it however, I have never really understood expanded ISO. The fact that the word expanded is used to describe the feature implies to me that its not real. So, my question is, if I switch from ISO 100 to 50, what is happening in the camera? There isn't less noise in the image is there? Is it just 100 with half the light allowed?
I would also like to understand what is happening at the other end of the scale. Not that I would ever, but what is going on at ISO 102,800?