3D television is the one that allows us to perceive depth, making the experience more realistic as we can see through the 3D TV screen as we do in real world, unlike when we watch TV in a conventional screen, where the images seem as if they were painted on a flat surface.
We perceive depth because we receive a different image in each eye. Since there is a separation between the eyes, each eye sees the objects from a different angle, and the differences in the images received in each eye lets us perceive the depth of each object; this is called stereoscopic vision.
When we watch 3D television, it is not possible to view the objects or the scene in the movie from different angles, as we do when we move around an object. When a movie or TV series is shot in 3D, the producers only take two views or angles of the scene; about enough to send a different image to each eye, but not enough to rebuild the entire scene from each possible angle. This means that if we are watching 3D TV or movies, and if we walk around the TV set, we will not be able to view the objects from different sides (there are other ways to accomplish this, but those are not used for TV. Refer to the 'related content' section to read more).
3D TV sets do not convert 2D traditional content into 3D content by themselves (some sets may offer a feature that says they do; it is open to discussion if the result is satisfactory). When used to view traditional 2D content, TV sets behave like any conventional TV set and display the content in a 2D conventional way. To view as 3D (that is, to perceive depth in the screen), the TV set must receive a 3D signal (you can read more in the 'What do you need' section).
There are some issues about watching 3D movies or TV with current technologies. The brain and the eyes have to accommodate themselves to the way the film is displayed; and even though the brain can understand it and perceive the depth effect, the fact that it has to accommodate itself means it may cause some stress in the eyes, and in some cases dizziness (this is discussed with more detail in the 'precautions' section).
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The most common technologies to view 3D images at consumer level are:
Anaglyph: which does not require special devices or subscription to 3D channels, but requires glasses with red and blue (cyan, really) lenses (or some other color combination). view more
Active technology: is normally based on 'shutter glasses', that operate synchronized with the TV set, and as the TV displays an image intended for one eye, the glasses block the image for the other eye; this is repeated many times each second, along the whole movie. It is called active technology because the glasses require to do some work to achieve the effect. view more
Passive technology: is normally based on light polarization; as the TV set displays two images with different polarization, each lens in the glasses allows viewing a single image if the polarization of the image and the lens are the same. This is the same technology used when displaying 3D movies in theatres. view more
There are some other consumer level 3D technologies currently in use, but these are not commonly used in 3D TV. The most common are:
Lenticular: it is used to display 3D images not only in screens, but in greeting cards, CDs or DVD covers, bookmarks and lots of other stuff. It works by sending images at different directions, so if each eye is in a different position, each eye may receive a different image. In printed format, the separation of images is made with a 'lenticular layer', while in screens the separation is made via a 'parallax barrier'. It does not require glasses, but is not widely used in 3D TV because it is not suited for use in large screens, mainly because the view of the different images for each eye depends on the position of the viewer; even though, when the technology was invented, it was used in large screens (which had issues because of this, like the 'Sharp Actius 3D' laptop), but works great in small sizes (like the Nintendo 3DS). Since it does not require glasses or additional devices, it is also called 'autostereoscopy'. view more
Dual screens: this is what is used in most virtual reality systems. It is not suited for 3D TV because since each viewer has to wear his or her own 'HUD' (heads up display), or helmet, or visor, or headset, is like if every person had to own his or her own TV set; also, while using the device, all field of view that is not related with the device screens gets blocked. view more
There are also some other techniques, but are not intended for consumer level, mainly because of their price, size of the setup and conditions of operation, so they are used in different applications, including research in different areas.
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So how far are we from 3D TV that does not require glasses?
The problem can be described like this: there are two images available, and each one must reach a different eye of some user that may be anywhere in front of the TV set. How do we project each image to the correct eye, in any space?
We are talking about a system that will project a different image for each eye, ideally, for an arbitrary number of users at the same time. As mentioned above, when shooting 3D movies or TV series, the scene is not captured from every possible angle, but from two positions only, about enough to send a different image to each eye. If many users are standing in front of the same TV device, and they could be anywhere around the TV, how do we know which image to send in which direction, coming from the same source?
The current state of the art is, there have been efforts to accomplish this using an equivalent technique to the 'parallax barrier' (refer to the 'lenticular' section), where up to 8 users can stand in front of the TV set and watch with no glasses; but the users have to remain in predefined positions. Instead of sending two different pictures, the TV emits 9 images that represent the Scene from 9 angles. If each user stands where he or she can view two different angles, then there will be up to 8 users that can perceive depth from different points of view. This is called 'Free Viewpoint TV', as it is an approximation of being able to view the scene from a (more or less) free position, and view the scene as it would be seen from that position. In particular, Philips released a model called 'WOWvx', but took it off the market after a while.
To display different images in different directions, the total resolution of the screen is divided by the number of users; some pixels emit the image in some direction, and some other pixels emit the image in some other direction. This means the total resolution of the set must be very high; also, instead of coding the scene as a series of 9 different pictures (one for each direction), the picture is encoded as two pictures (just like the stereoscopic pictures, or current 3D). It encodes the picture as a picture with the colors of the scene, plus a picture that represents the depth of each part of the screen (a height field); you can read more about this format in the 'related' section.
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Is 3D TV dead?
Since some big broadcasting companies have shut down some of their channels (BBC, ESPN), some people in tech blogs with wide recognition have posted articles with titles such as ‘the end of 3D television’, ‘3D TV is dead’ and so on. How truthful are those titles, besides of looking more like exploitation titles?
To answer that we should check which 3D contents are available and what people like to see. 3D got a huge boost after ‘Avatar’, so we can get from that that people like to see things in 3D, if they have something interesting to offer in 3D. Also, as in the case of Avatar, when movies are released both in stereoscopic 3D and conventional 2D, people prefer to watch the 3D release; yet not all movies are released as 3D. You probably won’t find listed any romantic comedy in 3D.
Also, when playing video games, people who have available the resources to play in 3D, often do so, even though not all the time; it is nice to see how the game looks in 3D, but after you have played some levels and all other levels look the same, you probably will return to 2D to play the remaining levels.
Production of 3D television is more expensive than 2D, for obvious reasons; if the scene is computer generated, it means you have to render it twice; once for each eye. If is live action, it means you have to edit twice and check that the final result looks good combined, so to sustain a 3D channel in a profitable way, you have to keep interested the audience, and have enough public.
If we are talking about a sports channel, say, a ‘football channel’, what would we see in the screen: we would watch the players moving across the field, in all transmissions. The field would remain the same in every transmission, and all transmissions would look the same. If you watch a game in 3D, the next one will not have anything different to offer in 3D, and you would be more interested in the score of the teams than in the 3D effect.
How about a soap, would it offer additional interest to the viewer if is displayed in 3D? or a politics debate in elections year?
People still prefer 3D in movies that are released as 3D in theatres, but those movies show different things than those that we see every day. They offer something to discover, and it is nice to discover those scenarios in 3D, to feel we are really there. This goes perfect with, for example, sci-fi, where they show us new scenarios from distant planets.
Once these movies are released for viewing in home-theater format, there are two options: either you can watch them in 3D, or you can’t (or you don’t want to), but if you prefer to have the option to watch them in 3D, it is obvious you require the adequate equipment. As David Katzmaier points out in his CNet article, one way to see this is that 3D is just a feature of the TV set; you decide if you use that feature or not.
Actually, we may say that 3D TV is dead (for the moment), besides of the intention behind sensationalist titles; we can not however, say the same about 3D content in general. 3D TV sets are the only way to watch 3D content (that has not been releasaed in anaglyph format, and since 3D is now a standard, anaglyph will probably be less common every day) even though that content may not come from a TV stream. There are more 3D BluRays every day, as most (if not all) movies that are released as 3D are later released as BluRay 3D. Same with video games: if the game system offers that feature (or PCs, for example the Nvidia 3D TV Play system), it will probably keep it for the next generation, so 3D content increases every day, even if that content is not related to football games. Just like there was an explosion of content when Internet became popular and there was a bubble burst of .com companies, 3D content has to be depurated and only worthy content will survive, marking the way for the kind of content we expect to see in 3D format.
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