Saw the Voyage of the Dawntreader (of the Narnia series). Most of the images looked rather flat, so I started watching without the 3D glasses. Turns out, much of the movie was in plain 2-D. It is cheaper to make, but you can sell it as a "3D movie" Yeah, sure. Never mind if it works or not,
3D IS NOT ON THE SCREEN MUCH OF THE TIME!

That is being "duped"

Next time the kids want to see a supposed 3D movie, I'm going to watch the whole thing without glasses and estimate just how much is in 2D.