For what it's worth smoke principally does NOT have a IR signiture. At least it doesen't absorb much heat. If I get really technical from a chemical sense who knows. Depends on the gerarator of the smoke. But back to my point. Has anyone tried photographing smoke with one of these filter thingies or with IR active film. I'm courious to know how it would work. Still planning ahead for the next 4th. ( To much smoke from the fireworks. ) bsteph