I'd like to make an object to be invisible to the camera, but still reflect lights (contributes to the reflection and GI).

For example I have a reflector setup like this:



But I'd like to make the reflectors invisible to the camera, while reflecting the light to the main character's face.

I'd say put down a render geometry settings LOP, and set the Render Visibility parm to "Invisible to primary rays(phantom)".

Unless I'm misunderstanding something.

raincole
For example I have a reflector setup like this:

There aren't any reflectors in that setup. Those are lights.