HI Harris,
It’s probably best to leave some magic and sorcery in the world of computer graphics…or even in real life…
This is rather complicated if you don’t know how a ray trace renderer works, but (quote from the Cycles Encyclopedia):
“If you turn MIS (Multiple Importance Sampling) off on a lamp, they will only be visible to shadow rays, meaning a regular ray will only terminate on emissive surfaces but not when hitting a lamp. So lamps will not be visible in caustics and sharp glossy reflections in that case.”
