I have been wondering this for a while, but I still am not sure yet about the answer. I have always read that the histogram extend from one side of the graph to the other in order to get the full amount of details and to capture the most light. But I have noticed that much of the time, my picture either looks washed out (overexposed) if the graph extendeds all the way to the right, or may look most realistic (look the same way as I see it in front of me) if it is only going from the left edge to the middle or just to the right of the middle. So my question is, is a histogram always supposed to extend to the edges, and if not is there some kind of rule that can be followed to know when to not take it to the edge? Maybe something like if it is a low light situation, the graph will be bunched from the middle to the left, in bright situations there may be no shadows, or just go with what looks best on the LCD?