This might be the wrong forum to post a question like this but I didn't know where to put it else.
What i want to know is how a ccd or a digital camera works in terms of ASA/ISO. For example the Arri D20 has a fixes ISO of 300 in its TechSpecs, but in the menu of the camera you can set different values from 50 to 400. So is it in the CCD/CMOS Chip or later in some electronical parts or the A/D converter where the ASA/ISO comes from? I searched the web but couldn't find something easy to understand or complete.