[dbttdft]

On second thought I think duration of persistence of vision (or afterimages) doesn't matter, but more the velocity of the object which your eye is following and the amount of angular "resolution" your eye can perceive. If your focus moves X amount while the object is lit, if that distance is more than the angular "resolution" your eye can perceive, it will appear as some blur behind the object.

You made me think about an interesting point I long avoided going into.