Everything you need to know about 3D TV

Baffled by all the jargon surrounding 3D? Not sure if your next telly should be 3D-ready? Fear not, we're here to take you through the essentials of 3D, explaining the terminology of technology's hottest topic.

So, how does 3D actually work?
Most of us have eyes spaced around 5cm apart. That means each eye will see any given object from a slightly different perspective. Your brain, clever stick that it is, combines these two perspectives into one complete image. This is called human binocular vision – and all 3D systems essentially mimic this process.

OK, so what are the different 3D systems?
There are two main kinds. The first is called the active shutter system. This works by alternately opening and closing each lens in the (battery powered) glasses, in time with a transmitter in the TV.

It does this very quickly – at least 120 times a second. The active shutter system is also known as frame sequential 3D, and it’s been adopted for 3D Blu-ray and 3D gaming on the PS3 (more on the PS3's 3D capabilities in Andy Kerr's blog). Technically, it purports to be the better of the two systems, as it supports a full 1080p 3D signal from Blu-ray and displays it correctly.

Sony's 3D active shutter glasses

And what’s the other system called?
It’s known as the passive 3D system. This creates 3D using simple polarised glasses, which do not switch on and off like active glasses, and are therefore considerably cheaper.

With passive 3D, the two images on the screen are circularly polarised in opposite directions: once you don the glasses – which have lenses that are polarised to match – each of your eyes sees only the image it’s supposed to. The result is a proper binocular image for your brain to decode – and with it, a glorious 3D picture.

Polarised 3D glasses

Sky will begin broadcasting 3D in October. What system will it use?
Sky is using a version of the passive system known as side-by-side. It’s comparatively easy to implement: you’ll need a new TV to view it, but not a new set-top-box, and it can be viewed on inexpensive polarised 3D glasses.

The system combines the separate left and right-eye images onto a single, standard 2D high-definition video frame. The TV deinterlaces the incoming images, and then scales each image across the full width of the screen, while the glasses ensure each eye sees only the one it’s supposed to see.

Sky will broadcast Premier League footie in 3D

Hang on, I thought you said active shutter was the better of the two?
Well, it is – in theory. After all, active shutter is the system that can deliver a full high-definition frame to each of your eyes in turn. Plus, almost all current 3D TVs use active shutter.

I sense a ‘but’ coming on: what’s the catch?
In a nutshell, cost. Sky isn’t using it because frame-sequential 3D can’t easily be broadcast – it’s so much more data-intensive – and active shutter requires the more complex 3D glasses that are much pricier than the polarised specs used in the passive system.

Are there any other problems I need to watch out for?
The first generation of 3D TVs has given rise to plenty of discussion about crosstalk. This is when picture flaws – ghosting effects, lack of edge definition – are created because the image intended for one eye is seen by the other.

This tends to happen only with active shutter 3D, and is due to a slight lack of synchronisation between the TV’s transmitter and the active glasses. Interestingly, the problem more commonly afflicts LCD TVs rather than plasma sets, due to plasma’s generally higher refresh rates. Panasonic in particular has declared it will only produce 3D sets, for now, using plasma technology.

Cloudy With A Chance of Meatballs on 3D Blu-ray

What else do I need?
You’ll need a 3D Blu-ray player, and an HDMI 1.4 cable: this is the latest generation of the connection standard, and supports all variations of 3D as well as super-high resolutions and the high-speed transmission, in both directions, of internet data.

Sony BDP-S570 3D Blu-ray player

Love 3D? Sit up straight!
That’s right, 3D viewing relies on proper posture. With some active-shutter 3D specs, even tilting your head to one side can cause the image to get notably darker – turn it to a full 90 degrees – or lie down, in other words – and the picture disappears altogether.

Panasonic’s plasma is an honourable exception, but even that isn’t immune to the other big concern with active-shutter TVs: eye-strain. Higher refresh rates – 240Hz or 480Hz – should help alleviate the problem. For now, many advise you don’t watch 3D for more than three hours at a time.

Gran Turismo 5: the world's most visually exciting 3D game?

Andy Clough

Andy is Global Brand Director of What Hi-Fi? and has been a technology journalist for 30 years. During that time he has covered everything from VHS and Betamax, MiniDisc and DCC to CDi, Laserdisc and 3D TV, and any number of other formats that have come and gone. He loves nothing better than a good old format war. Andy edited several hi-fi and home cinema magazines before relaunching whathifi.com in 2008 and helping turn it into the global success it is today. When not listening to music or watching TV, he spends far too much of his time reading about cars he can't afford to buy.