I have a carousel 4200 projector with an Ecktagraph 100-150mm zoom ff3.5 lens. The only way to get a slide in focus is to hold the lens abount 3-4 inches away from the projector, so the light goes thru it onto the wall. When I put the lens in the projecotr, it doesn't focus at all (I've tried from distance of 10 to 20 feet away from the wall). I get no image other than different color lights until I take the lens out of the projector - and then I get a clear picture. What could cause this? Before I spend money on a new lens (shorter and wide angle) or take the projector in to be fixed, I could use any suggestions. Thanks for your help!