OK, we need to get a rainbow effect on a plain backdrop. As always, way too short of $ and short on light fixtures. All our main Lekos are commited just to light the show. We have some very old HUGE 8" 1000 watt lekos without a pattern slot, several 500 watt fresnels and 2 follow spots. Looking for any suggestions before we start hanging lights. Anyone ever project from a prism before?