You're traveling through another dimension, a dimension not only of sight and sound but of cash. Indeed, the current holder of the highest-grossing film ever is a 3D movie, and this, along with the huge display of 3D home television sets in the 2010 Consumer Electronics Show, is a clear indication of the direction the industry is taking.

3D imagery has been around for ages, mostly as a gimmick, but things have changed in the past few years. The current incarnation of digital-quality 3D photography, combined with high-quality and distortion free viewing technologies, is finally mature enough to warrant an industry-wide technology and mindset switch. Right now, it’s all about movies like Avatar, but soon we will be looking at 3D games, websites and some day, everything else. How does all this stuff work? How will it affect our industry and our lives?

Our ability to feel the world around us in three dimensions is based on the fact that we have two eyes, and they are placed next to each other. This distance causes the images captured by the eyes to have a vertical shift relative to each other – if you are looking at a pole that is in front of a second pole, the right eye will see the 1st pole a little-more to the right than the left eye.

This is easy to notice if you look at something, and alternate closing one your eyes. The closer an object is, the bigger the horizontal shift will be. Our brain is “programmed” to automatically diagnose this slight difference, and unconsciously judge the distance the object is based on the amount of shift it notices.

3D stereo pair from 1936. (Courtesy Erez Ben-Ari)

For this reason, people with a damaged eye cannot judge distances correctly, and this is also why a TV image looks flat – we see the TV itself in 3D compared to the wall and TV cabinet, but the image itself does not have any “layers” of depth and look the same to each eye.

With 3D movies and photos, the photographer uses two cameras that are placed adjacent to each other, similar to how our eyes are. The end product is actually two films – one for the right eye, and one for the left.

Some films, BTW, are shot using a regular camera, but then graphic artists “convert” the film to two by manually cutting each image to layers, and then moving things around a bit, to simulate the shift that is required (as shown above). Some 3D photographers take still photographs with a single, regular camera, and they just take one shot, move the camera sideways a little, and take another shot. These techniques have been around for many years, and if you visit the Museum of Flight, you can see 3D images that were taken this way during World War II.

The hard part is replaying back these images or movies. The idea is to deliver the left picture or film to the left eye, and the right to the right eye. I won’t discuss all the various ways to do this, but the most popular way, initially, was to use the notorious red-blue glasses. This technique is based on coloring the left and right images and then imposing both on top of each other. Then, the glasses use the color filter to filter-out for each eye the image destined for the other. This way, the brain gets a shifted-image from each eye, and its built-in analyzer gives us the feeling of 3D.

The problem with this is that the color-filtering is not very accurate, nor is it very complete, and so each eye will often see a faint “ghost” of the image intended for the other eye. Also, the resulting image has distorted colors, which are particularly noticeable with blues and reds. There are variations of the same thing using other colors, like the movie Coralline, which uses Yellow and Cyan, but ultimately, this is far from a great solution.

A few years ago, a new delivery method came about, based on polarizer glasses. This technique is based on the fact that light can have a polarity. Imagine light waves to be moving along like the wing of a plane, which is normally horizontal. If the plane rolls on its side, like warplanes often do, the wing can be vertical. Normal light is a mix of waves that are both horizontal and vertical, as well as other angels, but using a special filter, one can block the waves. This is called a polarizer filter, and when you look at things through it, only light at a very specific angle comes through.

With 3D movies, we apply this filter at two angles to the two films, and then superimpose them on top of each other. This still looks fuzzy to the naked eye, but then, we put special glasses with matching filters on our face. The light for the left image comes at some angle and the light for the right eye comes at another angle. Both angles arrive at both eyes, but the filter on the left eye only lets the light at the 1st angle through, while the right filter lets only light at the 2nd angle through. The result is similar – each eye sees only the image that was designated for it. The filters are gray, so there’s no color distortion, and the filtration is very precise, so there’s good separation and most people don’t notice any “ghost” images.

A 3rd technique, employed by some of the home 3D TVs now headed for stores, involves synchronized active glasses. This technique is based on the fact that the image on the TV is refreshed at a high rate. As you probably know, a movie is a series of images that are projected rapidly, giving the illusion of movement. With 3D, the image sequence is alternating – one image for the left eye, and then one for the right, and back to left. The viewer wears electronic glasses that are designed to block the lens in sync with the TV. During the showing of the left image, the right eye is blocked, and vice versa. This is fast enough so that most people don’t feel the blanking at all, although some people have an adverse reaction to this in the form of headaches or dizziness. Another disadvantage is that the active glasses are bulky and expensive, so if you want to have the guys over for a game in 3D, prepare to spend a lot of cash.

The 4th technique is based on putting a special lens on the TV screen itself, which splits the screen into many vertical bars. This works similarly to “lenticular” images – the 3D images we can often find in printed advertisements. Each of the two images is split into thin strips, and the lens shows the “left” stripes to the left eye, and the vice-versa. The result is sweet, because no glasses are needed, but the problem is that the field-of-view is limited. Move a little to the right or left, and the illusion breaks, and might even cause dizziness from the bending of the light.

Which of all these will prevail? That is hard to say. There are currently many 3D movies that come with cardboard glasses and can be viewed on any TV, but the polarized glasses seem to be a cheap and good solution too. There’s a good chance that future models will support several technologies, because the forces behind them are significant. Another piece of technology that is likely to become standard is special computer software that can automatically convert regular, flat movies to 3D in real-time. The result is not perfect, but for many movies it can be quite effective. More about this next time!

Story and graphics by Erez Ben-Ari, a Seattle-area journalist and technology guru who has worked in the high-tech industry for more than 15 years, for companies including Microsoft and Intel. His written work has been published worldwide in the printed and online media, as well as television and radio. Contact him directly at ohlord@gmail.com. Previously: The science of electronic books, and the divide in digital reading

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