not a bizarre question today, but I would like to investigate a (sort of) myth in photography.
Sometimes I hear photographers saying that raising the ISO settings is the same of shooting in RAW at the lower ISO settings and adjusting the exposure in the RAW developer.
That means shooting at ISO 400 is like shooting at ISO 100 giving a +2 stop exposure while developing the RAW. Taking care of the image quality, is that true?
Beside this, I wonder how the sensor achives higher ISO settings... are they achived by multipling the digital data or by amplifing the analogue signal?