I'm far from expert here, but being as no one has offered a reply, I will give my interpretation of what I see in my new D5100. In any mode except M, the camera compensates the best it can. If you're in S mode, it adjusts ISO and Aperture. If you're in A mode, the camera adjusts ISO and shutter speed. Hence, the exposure meter is moot unless it falls off the chart and you need flash. In other words, you only see the meter when it can't make a good picture.