Some of this discussion relates to what the eye can see. An image will not appear sharp unless there is detail to the limit of your vision. For the average young person with excellent eyesight the "mark eight eyeball" can resolve features about .1mm apart. This works out to about 250 dpi. It is my understanding that magazine art is around 150-200dpi and fine art printing about 300 to 350 dpi. What confuses me is that it takes 4 spots of ink (CYMK) to create a dot doesn't it? So how does this work in when figuring print resolution?