Quote - Does it still work if you make the black square "invisible to camera"? Was just thinking in this instance that there'd be no way to render any part of a ceiling tho I guess most renders it's usually hidden ;).

 

Yes, it does. I've just tried and it works exactly as in the original.

If I point the camera at the light, and the black square, it looks kind of odd how the light is now lighting up the ceiling with a bit missing, but in real life that patch of darkness would be covered by the light bulb, fluorescent tube, lampshade, etc. That oddness is only visible because Poser lights don't show up as actual objects, but yeah... "Visible in camera" switched off definitely doesn't bring back the splotches.