Lighting to create the illusion of depth

I was reminded this morning about what a special guest speaker told our film class years ago. This person was talking about the coming wave of digital cinema cameras and how good they were in low light situations.  Little did this person know that they would get soooo much better.  This person went on to say something to the effect of 'you won't even really have to light anymore because these new cameras will be so sensitive in low light situations.'  What this person didn't understand - while holding the Oscar they had just won - was that we don't light for illumination alone, we light so we can make a 2-dimensional screen appear 3-dimensional.