On Wednesday, May 11, 2011 7:34:16 AM UTC-7, dadiOH wrote:

Procedure

1. Add up the total potential lumens from all bulbs

2. Divide the total by the area of your shop. You now have the maximum
light AT ONE FOOT FROM THE BULBS

3. Apply the inverse square law to determine light at work surface height.
a. at two feet from bulb, light will be 1/2...at 4', 1/4...etc.

That's overly pessimistic; firstly, the square law doesn't apply to
four-foot-long fixtures until you're over four feet away. Second, the
light will reflect from walls and floor and such, it isn't escaping into
an infinite void.

End-to-end fixtures (basically a long line of light) is best scaled
by an inverse-R law, not by an inverse-R-squared law.