Some say, "exactly like dragging exposure slider in Lightroom, ISO ... is just digital gain". With a few exceptions, this is less than a half-truth.
Though it is often the case that at higher ISO settings digital "gain" is applied (or a converter, using a metadata tag, is instructed to apply it), analog gain still acts first, before "digital gain" (the better word would be "multiplication", not gain, as in electronics "gain" most often pertains to analog domain).
The giveaway for multiplication is deep and regular gaps in the raw histogram that become wider with each increase of ISO setting.
