A sight for sore eyes?

3D TV technology has provided a buzz at consumer tech and broadcasting conventions - but calls are growing for research into anecdotal tales of eye strain. E&T investigates.

The buzz at both broadcast and consumer tech gatherings this year has been primarily about 3D movies. For the movie industry, it offers 'event movie' producers an opportunity to draw more punters in with the possibility of a seemingly immersive experience. It has also allowed cinemas to charge a premium on tickets for the privilege of wearing polarised lenses to experience 3D.

Jeffrey Katzenberg, CEO of Dreamworks, recently told an industry gathering: "In a business where margins are sinking like a stone in water, suddenly something comes along that for a small incremental investment can create huge incremental income. Why every studio isn't out making three, four, five 3D movies is inexplicable. I don't understand what they don't see."

For the consumer technology industry, it will also offer up a great deal of financial rewards because the current digital high-definition (HD) 3D technology will require viewers to shell out on the latest TV sets. You will require a TV that can broadcast in HD and also at 100Hz (on the PAL TV standard) or, better still, at 200Hz.

3D is also likely to be an important fillip for makers of Blu-ray players who have just announced the availability of 3D movies on the new format.

Broadcasters too are getting in on the act. British Sky Broadcasting recently announced that it will launch the UK's first 3D channel next year. The channel will offer a broad selection of 3D programming, which is expected to include movies, entertainment and sport. The service will be broadcast across Sky's existing HD infrastructure and be available via the current generation of Sky+ HD set-top boxes.

"3D is a 'seeing is believing' experience, making TV come to life as never before. Just like the launch of digital, Sky+ and HD, this is latest step in our commitment to innovating," says Brian Sullivan, managing director of Sky's customer group.

But a small contingent within the broadcast and content creation industry is beginning to take a step back and question the technology and the claims that are being made about it.

David Wood, deputy director general of the European Broadcasting Union, recently published a paper presented at this year's IBC, the industry's annual technical broadcasting convention, questioning some of the claims made about 3D movies. He suggested that there ought to be more research conducted into the health effects of viewing 3D movies for lengthy periods - particularly as much of the content is aimed at young children.

3D eye strain

"I'm a big fan of 3D technology. It's just I'm concerned by the lack of medical research into much of the anecdotal evidence of eye strain - and this is particularly important if we are expecting the general public to view 3D in their own living rooms," Wood told E&T at IBC.

Wood believes there to be three generations of 3D TV which will progressively come into play in the future. We are currently in the first generation of 3D cinema where the viewer needs glasses with our brains doing the donkey work to give the image depth perception.

But the next-generation 3D systems would record several pairs of signals and present them on a display in the same way that old-fashioned lenticular prints work. With this method, there would be no need for glasses (the display would be autostereoscopic). The main limitation would be significantly lower resolution compared to current HD.

In fact, Wood believes that we will eventually move towards a system where we will record the entire light field or object wave. The 3D image would be perfect and, more importantly, no eye strain. However, due to the limitations on broadcast transmission rates and computational power, it would be anywhere between 30-50 years before we reach this stage.

But today, the industry has to work on a way to make the displays palatable for everyone who can perceive depth. In order to do this, content creators, broadcasters and manufacturers will have to ensure quality of the image on the TV screen. With 3D, there will be no room for poor compression technologies causing artefacts (the blocky effect that you sometimes get with digital transmissions).

A common standard would help, but as is the case with all new consumer technologies, a number of competing standards emerge with a great deal of information and misinformation aimed at the consumer.

One standard uses polarised filter lenses, which is essentially the same technology that is used in modern digital 3D digital cinema projection. This standard appears to be gaining the upper hand. Recently, the Blu-ray Consortium agreed to a 3D standard for Blu-ray discs. The manufacturers have opted for the passive system over the competing active shutter glasses - which transmit a compatible image for each polarised in quick alternating succession.

The alternative standard uses active shutter lenses. A signal is sent to the goggles in order to shut off one lens while the screen corresponds to the other lens - and vice-versa. Although more complex, this standard has strong backers in the form of Sony, LG and graphics processor Nvidia who plan to support 3D games using this method.

Whatever standard is chosen, both essentially transmit a slightly different image in each eye. Therefore the problem of vision fatigue is equally relevant for both sets of formats.

Stereoscopic displays

There has been a great deal of research into industrial and military applications of stereoscopic displays. After all, you would not want a jet fighter pilot feeling queasy if viewing his cockpit instrumentation through a visor. 

There is even a scientific method of evaluating 3D fatigue - the simulator sickness questionnaire. This rates a subject's physical response to 3D simulations - such as fatigue, headache, eye strain, nausea, blurred vision, sweating, and elevated salivation.

However, no-one has discovered a conclusive reason why these physical symptoms manifest in a small minority of binocular capable subjects.

One theory is the unnatural eye movements stereoscopy burdens viewers with. In the real world, our eyes rotate in two ways to perceive depth. Our eyeballs move inward towards our nose the closer the object comes towards us (vergence). At the same time, to keep the subject in focus, we adjust the shape of the ocular lens - like a camera (accommodation).

Therefore, when we watch a 3D movie, our eyeballs move inward as normal, but our lenses also want to change their shape to adjust to the plane of vision - but in reality the object has not moved even an inch closer. If it did, the entire movie would become out of focus.

These facts appear to be recognised by a number of suppliers of video content editing suites at IBC. One says: "The film makers are learning that they cannot have as much extreme movement in blockbuster movies."

Thus, the current auteurs of handy-cam style footage is likely to have to learn a new movie lexicon to ensure that their thrill rides are not vomit inducing.

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