3D Vision

• Your eyes can see in 3D because they're set a couple of inches apart so you see things from two perspectives. This is called binocular vision, but films are made on single-lens cameras that see in monocular vision. Theater and home screens are also flat, so displaying a 3D image requires tricking your brain. To trick you into seeing a 3D object on your screen, your left and right eye need to see slightly different images but on the same screen. That's where the 3D glasses come in.
  
  

Shutter Lenses

• Your TV and computer screens refresh the image numerous times per second. You don't see this, because your eyes see at a slower refreshing rate. If you try to videotape a TV screen with a camcorder, you'll notice a rolling image on the screen, which is the image being refreshed. A screen compatible with shutter images displays the left eye image on one refresh and a right eye image on the next, alternating rapidly. The glasses are filled with a liquid crystal that alternately opens and closes the left and right lenses at the same rate as the screen, separating the images.
  
  

Shutter Drawbacks

• Unfortunately, active 3D technologies all require an equally active power source. These glasses have to include a small computer chip that controls the lenses, an infrared system to synchronize the shutters with the screen and a battery--unless you want to be wired down to your couch to watch a movie. The other major downside is the cost: You can expect to pay $50 to $100 for a decent pair of shutter glasses.
  
  

Anaglyph Lenses

• If you've ever looked at the world through an actual pair of rose-tinted glasses, or glasses with any colored lenses, you will notice that some colors seem different through them. A red lens, for example, filters out red light, making any red objects you would be looking at appear white--and pulling red light out of other images. An anaglyph picture displays a red image and a blue or green image at the same time, with the left perspective tinted blue and the right slightly red. Each lens filters out the other eye's perspective, making the image seem three-dimensional.
  
  

Anaglyph Drawbacks

• Despite having a huge cost benefit--you could easily make your own pair of anaglyph glasses at home--this style of 3D imaging does have one large drawback: color. Because it filters out the red and blue light onscreen, this kind of film will work only if it takes out the colors that are supposed to be in the film. Most anaglyphic films appear black and white or have a limited color palette as an unfortunate result.