If I am photographing a scene with a lot of dark background, how can I use the histogram to tell if the exposure is correct? For instance, at an outdoor concert in which the performers are moderately illuminated but their surroundings are dark. Or a view of a cityscape viewed across a dark body of water and with a dark sky above it? In other words a scene in which much of it is expected to be almost or totally black. When shooting RAW in such a situation, what should the histogram look like to make the final processed image dark without being noisy? And without the black areas becoming posterized?