Here's what I'm trying to achieve:

1. Dark indoor setting in a room. Two characters facing each other. It is an intense confrontation.

2. From the ceiling shoots down an 8 foot wide column of light, as if moonlight were shooting through an 8 foot diameter hole in the ceiling.

The column of light falls on these two seeming advesaries but not so intense as to wash them out as they are standing half in and half out of the column.

 

How would I get this column of light (the column doesn't have to have a sharp, defined edge to it, however) to be a column? We don't have to see the source of the circular pillar of light, just its emanation, cutting throught the dark to the carpeted floor.