When deliberately shooting at a man-sized character model, either on foot or cavalry, there is a -1 to hit penalty as described in the Shooting section. This is because the normal chance of hitting assumes the target is massed up in ranks. This is not the case when you are shooting at a single character, especially if there are other potential targets to distract the shooter's attention.

Note that this -1 does not apply if you are shooting at a character who is riding a large monster as described in the Monsters section. In such a case the shooter does not suffer the -1 penalty and benefits from the + 1 to hit a large target as well.