I just checked - all my lamps were on inverse linear after all. With inverse square, the close proximity to IDL objects creates the splotches in my scene as well.

Inverse square is the more correct one, but only if Poser implemented a minimum distance cutoff clamp value. This would fix the problem. Real lamps are not point sources, and they do not become infinitely bright - inside a certain radius you are no longer looking at a single point but a gigantic bulb (from the point of view of a nearby fly).

I don't know why they left out this simple solution: The exponent should approach -2 (inverse square) at larger distances, but approach 0 (constant) at smaller distances, with a suitable blend in between. This would neatly approximate the reality of a light bulb, while still using a pointer source geometry simplification.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)