[cleeus]

Increasing the ISO is just a multiplication of the raw sensor value - it doesn't lead to more noise - it just makes it visible to the human eye. Also on my DSLR I can see all kinds of stripes and cross patterns in the noise, so a lot of it is not really random but based on static sensor properties.

[brndnmtthws]

Fair enough, it is indeed just an amplifier, but what I was trying to say is that the noise becomes quite visually apparent when you increase the ISO.

[iotscale]

you can cancel out static noise with multiple readings