Screen brightness too dark after taping iSight camera

Hi

I want to be sure not to be filmed by anyone making use of my iSight camera.

So, I disabled iSight with iSightdisabler.

Additionally I taped the camera with a little piece of paper. (There was still a small redish light in the camera).

The screen is too dark now. As soon as I take the paper away the screen is bright as always.

Why and where is there a link between the camera and the screen brightness? Calibrating is no solution.

Regards