Verification for 1/ (distance squared) value of light intensity with desk light and basic lux-metre
distance (in meters)	1/ dist square of dist	substracted ligth value	raw light	1/R^2 expectation
0,5	4,00	616	618	616,00
1	1,00	138	140	154,00
1,5	0,44	65	67	68,44
2	0,25	37	39	38,50
3	0,11	19	21	17,11
4	0,06	12	14	9,63
	substracted light value (lux) = measured value - measured background
	in a partly occulted room, the background was reasonably uniform at 2 lux
31-oct-06	jmf