When playing Fallout NV (I just started) its seems that out in the wasteland, I can see the red indicator on my compass so I can tell there is an enemy there, but when I look in that direction the monster/NPC doesn't appear until I'm fairly close. So far, it's been a little annoying when enemies suddenly pop out in front of me. My graphic settings are on MEDIUM at the moment, although my computer could still do better. Do I need to just adjust the visual settings higher or is it more complicated than that?

Oh and also, when I'm looking at an enemy (which I actually can't see at the time) I can use VATS and then the monster will appear, but I still shouldnt have to do that in order to see nearby enemies. - Just in case that helps.