Awesome. Some free time appeared suddenly, so I dug around on the topics of Quad and Distance, and found out the following from www.ee.oulu.fi/~kapu/cg_course/blenderkeys.txt :
When a lamp is not of type quad, the falloff works like this:
Intensity = Dist / ( Dist value + d)
where d is the actual distance from the light to the point being lit, and Distance is the value in the Dist field. I am sure the the intensity gets multiplied by the light energy.
When a lamp is a quad lamp, it goes like this:
Intensity = Dist / (Dist + Quad1 * d + Quad2 * d^2)
If Quad1 and Quad2 are zero, there is no distance falloff. However, using Quad lamps alone, it is not possible to duplicate the physically correct inverse square lighting that Lightflow uses. Instead of X / D^2, you end up with something like X / (X + D + D^2).
Sphere? I have no clue what that does. It looks like the lights MIGHT obey the inverse square law when Sphere and Quad are on and both Quad1 and Quad2 are equal to zero.
Does anyone know the nitty gritty math behind Sphere?