just for your info, I re-did the math myself.

For a disk-shaped lightsource (as a pointlight with some size at a distance), with radius R lighting a sensor at distance d, the light captured by the sensor is directly proportional to { 1 - 1 / sqrt(1+ R^2/d^2) }.
Just fragmenting the disk into tiny inverse square pointlights, and integrating over the disk.

Close to the disk, lighting levels become constant and far from the disk they become inverse square:

d = 0.1R, L = 0,90
d = 0.2R, L = 0,60
d =    1R, L = 0,30
d =    2R, L = 0,10
d =  10R, L = 0,005
d =  20R, L = 0,0012
d = 100R, L = 0,00005

Similar math holds for calculating lighting levels in streets having large shopping windows shining on the pavement. Constant near the shops, inverse square at large distance, and about inverse linear in between. That's why software like Poser offers all these three options for light attenuation, btw.

Now the issue: why is Poser IDL producing splotches, and what to do about it?

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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