>In flash photography light falls off - looses intensity- at the >rate of the reciprocal of the distance squared. 1/dē > >I wonder if with low intensty lights like florescent tubes, >that even if you used mirrors to reflect the light, is there >enough energy left to be even worthwhile. ?? I remember seeing on a web page (Lynn Edwards?) a fairly thorough discussion of light intensity. I think your formula is correct for a point source (flash bulb), but it is different for line sources (flourescent tubes). Scott... KCK