If you find yourself squinting at the theater, it might not be because of the standard plot holes and hacky exposition. It could be the lens of the projector. The Boston Globe reports on an unfortunate trend in some big movie chains where rather than swap out the 3-D lens when showing a 2-D moving, they leave it in place. The result can be an almost 85% darker projection, and should have audiences throwing popcorn at the screen. So how do you detect if they’re showing the movie improperly, while still charging you full ticket price?