I have noticed recently that when I was shooting some city shots at dusk that the blacks and dark sky would get some heavy noise. I was exposing for the street lights and buildings but all my shots in the dark areas started to look weird. I also just tried shooting a black board with a glass and the black starts to get the same look. How do I stop this or is this just what a digital sensor does. I was shooting at iso 100 for the photos. In other words how do I expose so that by black stays completely black without noise going nuts. You can kind of see it in this example but its weird in lightroom its very obvious but when i export into jpg it looks much better.