Try deleting all lights then turn on Deph Cueing in the preview (three bals at the botton of the viewport) go to render setings and select the Poser 4 tab unchek everything and chek Ignore shader tree, go back to the preview go the Render tab, where it say Firefly select Poser 4 then render, anyway it does work the way Bagginsbill says, maybe you just need to set diferent values for DephCue_StartDis (I allways set it to 0) and for DephCue_EndDis (in my test renders for this answer I used 2000)