John,

 

just read my posts above and look at the graph.

in the real world it hardly makes a difference for lightbulbs unless fixed to the wall, but it sure does make a difference for light coming from shopping windows in a street, as "about three times the radius" (or window size) is enough to cover a pavement along the shops, but from halfway the street itself things start to be inverse square again.

- - - - - 

Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though