If all combinations of fstop and shutter speeds that give the right exposure are the same why bother? Because grasshopper they aren't really the same. They might all give the same amount of light but all light is not equal. And neither is the speed of a shutter. So lets to that nasty old aperture thing first. Now you have to trust me, on this or try to relate it to that water faucet again, a wide open aperture Ie 1.4 2.8 ect produces a sort of spray effect. Getting light everywhere even over lapping here and there. This creates a very short depth of field or of course the inverse is true. A small aperture IE 16, 22, 32, 45, 64, 128 create huge depths of field. So what is depth of field and why do I care. Patience grasshopper that's next lesson. There is one more part of this one to go. A fast shutter speed stops action. So all shutter speed is not the same. Slow shutter speed allows movement to show as slur also if the shutter speed is long enough moving objects disappear. Why would I want that? you are trying to get ahead of me now. If you have anything to add or questions pop right in here.