A Beginner’s Guide to … 3D entertainment
Don't know your passive display from your active glasses, then read on for everything you need to know about 3D.
Without the glasses, the TV shows a Full HD 1920×1080 picture. However, when viewed through polarised glasses, the picture is split, usually per horizontal line, so that all the odd lines go only to the left eye, and the even lines, only to the right eye. As such, each eye sees a 1920×540 picture. Active shutter glasses, on the other hand, show the left eye a complete 1920×1080 picture, and then the right eye another 1920×1080 picture.
That said, a new technology, from RealD who designed the system in cinemas is coming. This is best described as active polarisation, with the screen actively switching between differing polarised images. The idea is to get the full screen resolution with cheap polarised glasses – though we’re yet to see it working in practice.
JUST BE CONTENT
None of these 3D TVs are much use without 3D content to show on them, and that’s been slow coming. Sky’s 3D channel, appropriately named Sky 3D is available to subscribers of its HD packages, although it won’t add anything to their bills. A quick glance this week shows that content is largely limited to sports, animated movies and music and dance programmes. Victoria Etaghene, Consumer PR for Sky told us, “As more content is available for the channel we may look to change the way we offer it to customers.”
Football fans in Cardiff getting a preview of Sky’s 3D sports channel
Sky first unveiled its technology back in January 2010 when it broadcast live coverage of the Arsenal versus Manchester United football match to nine pubs around the UK. We’ve had a number of chances to view the service since then, and although football in 3D doesn’t immerse you in the same way as it does at a cinema, the effect is convincing. Shots from the stadium terrace give the impression of being there in person, and views from the touchline provide an amazing sense of perspective.
Sky has had to find a way to broadcast its 3D service using its existing satellite network and Sky+HD set-top boxes. Dual TV cameras capture a pair of images, but these are squashed so they fit side by side in a normal 1920×1080 HD signal. This passes all the way to the TV, whereupon the 3D TV expands and overlays the left-eye and right-eye images to show on the screen for the 3D-bespectacled viewer. This means that the resolution is halved to 960×1080, but that’s a fair price for not needing a new set-top box or a change to the Sky infrastructure.
If you’ve tried watching 3D TV in a pub, then the chances are the screen will use polarisation, halving the resolution that reaches your eyes. Factor this with Sky’s 960×1080 broadcast, and you’re left with a 960×520 picture for each eye – just a quarter the resolution of 1080p Full HD. So if the details were a little soft then you’ll know why. Thankfully, the benefit of 3D effect is far more significant, and TVs that use active shutter glasses can display Sky 3D’s 960×1080 broadcast without wasting any detail.