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What is 3D TV and does it still matter?

The appeal of 3D may be waning but there's still plenty of good content out there

by Steve Withers Oct 22, 2014


  • Back in 2010 all the manufacturers were talking about how important 3D was going to be.
    Four years later it's clear that 3D never turned out to be the saviour of the industry that those manufacturers hoped it would be and, generally, people are uninterested in 3D at home. There is still a degree of popularity for the format at the cinema, although even that is waning, but, as it turned out, consumers were largely adverse to wearing 3D glasses in their lounge.

    The consumer electronics industry has moved on and now Ultra HD 4K is the big new thing but, despite that, most new TVs do support 3D by default. So that means if you're interested in the format or perhaps just fancy trying it out, all you need to do is get hold of the appropriate glasses for your TV (it may even have come with a couple of pairs).

    So in this article, we'll take you through the two differing ways of watching 3D, explain how they work and their strengths and weaknesses. We'll also tell you were you can get 3D content, what to look for in a 3D TV and how to set your it up properly so that you can get the best out of your three dimensional experience.

    What is a 3D TV?


    Well put simply, it's a TV that can show 3D content using either passive or active glasses. It doesn't matter if your TV uses a plasma, LCD or OLED panel, if it supports 3D it will be either passive or active. Whichever method the TV uses, the way it creates a 3D image is essentially the same. All 3D TVs display two images and by wearing a special pair of glasses the two images are split so that each eye only sees one of the two images. It is as simple as that but where the clever part comes in is how the brain interprets these two images. When comparing these left and right eye images, every object in the scene is horizontally displaced by a small amount.

    The brain assumes these two displaced objects are actually one object and tries to fuse them together. The only way it can do this is to assume that the object is either in front of or behind the screen. The direction and the amount of displacement define where each object is in the 3D space. The wider the displacement, the further behind the screen the object appears and conversely the narrower the displacement, the further in front of the screen the object appears. When it comes to the glasses that are used to differentiate these images there are two approaches - passive and active.
    There are two approaches to delivering 3D in the home - passive or active.

    What is Passive 3D?


    In its simplest terms the passive 3D approach uses a pair of polarised glasses and a polarised filter on the front of the TV screen. You can’t normally see this filter but when you put on the glasses it ensures that each eye sees alternate lines of the high definition picture, creating a discrete image for each eye that the brain then combines to create the 3D image.

    The big benefit of this approach is that the glasses are cheap and, in fact, if you have any RealD 3D glasses that you brought home from the cinema, you could even use those. There is also no flicker, less crosstalk and the passive glasses don't need batteries or recharging, making them lighter and less prone to damage. The downside is that because each eye is only seeing alternate lines, the vertical resolution is reduced. However whether you will really notice this will depend on where you sit and the quality of your eyesight.

    Although if you own an Ultra HD 4K TV that uses passive 3D then you will actually get Full HD for each eye thanks to the higher native resolution of the panel - 1080 lines times two which adds up to 2160. The biggest supporter of passive 3D has been LG, who refer to their version as Cinema 3D, but most of the other manufacturers, with the exception of Samsung, have released one or more passive 3D TVs.

    What is Active 3D?


    The alternative approach is active shutter 3D, which uses glasses that have LCD lenses synchronised with the images being displayed by the 3D TV. Each view is displayed on the screen sequentially and, thanks to a battery in the glasses, when a small electrical current is passed through the lens it goes dark, thus the left eye sees the left eye view whilst the right eye is blacked out and vice versa.

    This process synchs the 3D TV to the glasses via an IR (infra-red) or RF (radio frequency) emitter and the alternating views are shown hundreds of times a second, so that once again the brain combines the left eye and right eye views to create a 3D image. The main advantage of active shutter 3D is that you get the Full HD image in each eye, so the resolution is higher than passive 3D.

    However there are also downsides, the glasses are more expensive, less robust and they require recharging or new batteries. One of the other big downsides is that due to the glasses opening and closing quickly some people can see them flickering, which often causes fatigue. Active shutter glasses can also darken the image more than passive glasses and can be more susceptible to crosstalk or ghosting.

    Which 3D TV should I buy?


    Well since most new TVs support 3D, it largely comes down to deciding which type of TV you want - LCD or OLED - and whether you want to go passive or active. There's also the added question of resolution, do you want to take the plunge and get an Ultra HD 4K TV or stick with good old fashioned Full HD. What you ultimately decide is going to come down to preference but with plasma no longer being produced and OLED still in short supply, the chances are that you'll be buying an LED LCD TV.

    Probably what is more important is the screen size you choose because the larger the image, the more immersive the 3D experience. If you decide that you want to go for a larger screen size such as 65 inches or bigger, then you would probably be better off choosing active shutter 3D or an Ultra HD 4K TV that uses passive 3D. However for smaller screen sizes, passive 3D TVs can be very effective and are often more common.
    Which type of 3D TV you choose will largely come down to personal preference.

    Where can I get 3D content from?


    Once you have decided which type of 3D TV and which method of 3D delivery is best for you, then next question is how to source 3D content. After all, there isn’t much point having a 3D TV if there’s nothing to watch. There are a number of methods for delivering 3D into the home, including digital off-air, satellite, cable, the internet, video game consoles and Blu-ray players. There are two basic ways of delivering 3D into the home and these are called ‘side-by-side’ and ‘frame sequential’.

    The side-by-side method is more commonly used by broadcasters and if you have watched 3D broadcasts by SKY or the BBC you will literally have seen two images side by side. Those two images are the left and right eye views, which the 3D TV can detect and then display as a 3D image and the reason this approach is good for broadcasters is because the bandwidth and frame rate are the same as a normal transmission.

    Unfortunately the downside of this method is that the horizontal resolution is halved for side-by-side broadcasts which can give rise to jaggies in the image. As it happens this is largely academic these days because, due to the failure of 3D to gain popularity, the BBC has abandoned its 3D broadcasts and even SKY have curtailed their broadcasts as well. It is likely that as Ultra HD 4K increases in popularity, all broadcasters will ditch 3D in favour of ultra resolution broadcasts.

    The other method is frame sequential which is good for local connections such as Blu-ray players and game consoles, both of which can handle the higher bandwidth required. Frame sequential 3D, as the name implies, consists of a sequence of alternating frames wherein each successive frame carries the image meant for one or the other eye. This means that if the first frame contains the image for the left eye, then second frame carries the image meant for the right eye, the third frame again carrying the image for the left eye, and so on.

    This format has proved popular because unlike side-by-side, it can deliver Full HD 3D and for this reason it is part of the 3D Blu-Ray specifications. There are a large number of 3D Blu-rays, with more released every month, so Blu-ray has become the single biggest source of 3D content and it is also the best, delivering highly detailed and Full HD images. There have been some games released that support 3D but the format generally failed to catch on with gamers and is no longer really supported. So 3D Blu-ray remains the primary and best source of 3D content.
    The primary and best source of 3D content are Blu-ray discs.

    What about 2D to 3D Conversion?


    There is of course one final way of creating 3D content and that is using the 2D to 3D conversion feature included on many 3D TVs. However be warned, this is not real 3D but an approximation created in real time by algorithms built into the software on the 3D TV. As such it is very unrealistic and prone to errors and artefacts when the convertor becomes confused by the original 2D image. Here at AVForums we feel that the 2D to 3D conversion features on 3D TVs are little more than a gimmick and best avoided.

    How should I set up my 3D TV?


    In terms of setup, the approach for 3D is exactly the same as it is for 2D. So you should concentrate on getting your TV accurate in terms of greyscale and colour gamut. You should follow the guidelines in PIcturePerfect and try and choose the Movie, Cinema or THX mode where applicable. If you have a THX certified TV, there will be a THX 3D mode that has been optimised for 3D but most manufacturers will create a Movie or Cinema mode for 3D signals as well as 2D. The big difference between 2D and 3D is that in 3D you need to boost the brightness more than normal. This is because when watching 3D content, you are essentially wearing pair of sunglasses, so the brighter your image the more impact it will have.

    Is 3D still relevant?


    In general terms, not really. The majority of the public are largely uninterested in 3D at home and in the US many studios don't even bother releasing movies on 3D Blu-ray, even when a 3D version is available. A lot of 3D films these days are post-production conversions but are aimed at the Asian market where 3D is still hugely popular. However amongst enthusiasts 3D remains a must-have feature and there's no denying that when do well, a 3D movie can look great at home. Ultimately it will come down to the individual but the chances are your new TV supports 3D and there are hundreds of 3D Blu-rays available, so why not give it a try? If you're unsure of what 3D Blu-ray to get first, take a look at our handy guide.


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