Invisible for Camera option? Cliplane?

[mbetke]

I searched the forums but had no luck. Is there a way to hide an object from camera? I want to render a room with proper light inside but the ceiling needs to be invisible because the camera looks down into the room.

Opacy makes the light shine into the rooms. What can I do? I tried to check the "hide" option in my 3d app but it doesnt work. With Mentalray and Maxwell I can do it easily. I hope Octane can do it too with a special material setup or so.