I'm beginning to use Manual mode on my Nikon D5000. In my high school days, I was a big Auto guy, and recently I've been using either A or S priority modes. I understand metering, and I am ok with compensating either shutter speed or aperture to get exposure. What I'm struggling to understand is when you would choose to use either shutter or aperture, and how you decide on adjust one over the other. To me, it has to do with adjusting the shutter for moving objects vs adjusting the aperture for depth of field....but it can't be that simple can it?