Indeed even the latest digital camera relies on the separation method to capture light.

BBC: Pioneering colour photography

"A Separation" is its own shining light.

WSJ: A Separation | War Horse | Iron Lady | A Separation Comes Together Exceptionally | Film Review by Joe Morgenstern

That light switch introduces a middle man, a layer of separation between the action and the thing you really want to work on, which is the light.

FORBES: Thanks Buttons. Touch, Speech and Gesture Can Take it From Here