A couple of RAW questions...
ISO affects the electrical gain of the sensor. Higher sensor gain requires fewer photons to achieve the same digital value. It is similar to turning up the gain on a microphone pre-amp, you get more background noise at higher gains.
This is not the same as amplifying the gain digitally during raw processing. The ISO setting affects the electrical operation of the sensor, which in turn affects the digital output.
|Waffles with fruits by Coolinarka|
from Food photography (desserts)
|Vestrahorn Frozen Reflection by Will B Milner|
from Ice cold