Why isn't 3D TV "worth it"?

It turns out 3D tvs are not selling very well. This isn't really a surprise to anyone since nobody wants one. If you ask people why they don't want a 3D tv they will give some general excuses about how it's just not worth it. It's the reason why it's not worth it that i find interesting.

People liked HD. People looked at HD content and saw that it was better. Our eyes are higher resolution than a tv screen (probably even higher than a retina screen depending on the individual) and a higher resolution image appeals imediately to us. People also like the wider aspect ratio. Humans have a field of view that is wider than it is tall. A widescreen display fills more of our field of view with what we are interested in.

People also have depth perception. We live in a three dimensional world. We should see 3D as another step closer to reproducing a vivid immersive experience. Obviously, people don't think it's a step worth thousands of dollars. I don't think it's just the economy though. I think there is a deep rooted reason why 3D just isn't that compelling.

Our brains are very good at extrapolating depth information from a 2D image. When we watch TV, we don't need to analyze the image to determine the spatial relation between everything in the scene. We know Knight Rider is driving right at us. We know Don Draper is standing right next to his secretary. We get 99.9% of the information in a scene from a 2D image. The third dimension adds so little extra information that it's not worth having.

I think our brains don't even like consuming 3D content. Technically, they don't. Our retinas are essentially 2D. They are spheroid in shape, but covered with a 2D array of sensors. Essentially our brains recieve a 2D image from each eye. We rapidly compare differences in the images and deduce depth information from it, or do we?

It's actually really easy to fool our depth perception. A room with one end slightly wider than the other will appear longer or shorther than it actually is. In an Ames room, it's often impossible for us to tell what's going on. If our brain comparing 2 images was all that gave us depth perception, we wouldn't be tricked. Someone at the other end would generate the same delta in the two images as someone standing 20 feet from you. it would require the same focal length as someone standing 20 feet from you, but your brain will tell you that they are a tiny person standing 10 feet from you. The trick works because lines you expect to be parallel are not. Data from the 2D projection of the scene overrules the 3D information.

It's just as easy to trick your brain into thinking it's seeing 3D content when looking at a 2D plane. Essentially TV does this all the time, but certain works really take advantage of our brain's extrapolation of depth. Again, the information coming from two eyes should overrule the illusion, but it's almost impossible to not be fooled. Most people have to concentrate to see a flat image.

Under certain situations people find it advantageous to force a 2D view of the world. Weapons are far easier to aim with one eye. landmarks are easier to line up when surveying. If you close one eye and try to walk around the room chances are you will be more bothered by the loss in your field of view than a lack of depth perception. In fact, the only time i ever hear people complain about not having depth perception (i have friends with bad astigmatism) is in regards to 3D movies and how they can't see the effect.

So how much of this is learned and how much of this is instinctual? In school, some of my teachers would recant stories of people in primitive cultures being unable to make sense of photographs and drawings because they never learned to see in 2D. That would point to our preference for 2D television being more a learned behavior than an inborn view of the world. Those stories are at odds with some other evidence though. There are numerous conflicting anecdotes of primitive people fearing a camera stole part of the subject's soul. Clearly those people recognized what the photograph was.

We know people represented the world in 2D long before there was television. Cave paintings are good evidence that people who never watched tv could work out how to project items onto a 2D plane. People have made paintings for a long long time. Prior to the advent of vanishing points and a mathematical understanding of perspective, painters made crude attempts at reproducing it. They seemed to understand that it was possible to represent the depth of a scene in a 2D plane. The instinct was there if the technique was not.

Maps are another very interesting 2D projection. People find them easier to use because they discard a useless third dimension. Even in 3D video games, players are often provided a 2D map to navigate by. It's almost like it's easier to consume the 2D content.

I really think our brains are wired to store and recall the world in 2D. How many of our memories can we zoom around in and reconstruct the scene from any angle? It's REALLY hard. I think 2D content on tv is more than just convenient. I think it appeals to our brain as it comes in the tasty form of instant memory. It's like a window into the world the way our brain likes to think of it.

Of course maybe we just like 2D content because we grow up watching TV. I don't really know. It sounds like the people making 3D TV's should be asking if 3D content can ever really be compelling.