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Introduction and Active Tech

John Archer


3D TV Buyer's Guide - Display Hardware

If you thought the confusion and chaos that surrounded the arrival of HD TVs and HD disc players was bad, you ain’t seen nothing yet. For the more 3D starts - supposedly - to go mainstream, the more insanely confusing it seems to get.

This has become more and more obvious with every passing week, as we’ve found ourselves almost routinely having to explain new facets of 3D technology in the course of our regular AV product reviews.

So the time seems right to pause for a moment to reflect on where the whole 3D bandwagon has got to.

There are essentially two sides to the 3D-at-home story: the display hardware (TVs, projectors) and the 'software' - as in, the different 3D production formats used by the various 3D content providers. Today, we intend to focus on the hardware.

The 2011 Consumer Electronics Show in Las Vegas was awash with 3D TVs. Which was, of course, no surprise. What was rather shocking, however, was that rather than seeing a unified move toward a single 3D screen standard, as expected, the major brands actually split into three fiercely competitive and totally different 3D camps: active passive and glasses-less.


The active format was the one we’d expected to find everyone lining up behind. It was certainly this one, with its ability to deliver full HD 3D signals, that dominated 2010’s 3D scene.

Samsung UE55C9000 'Active' 3D TV

Active displays work by displaying whatever 3D source format they receive as a series of ultra high speed frames, designed to be shown sequentially to each eye. One full resolution image is sent to the left eye, then the other ‘half’ of a stereoscopic 3D image is sent in a separate full resolution frame to the right eye - all so quickly that your brain puts the images together to create a 3D effect.

To make the system work effectively, active 3D displays require you to wear electronic glasses featuring built-in ‘shutters’, so that the eye that’s not being sent any information can be shut off from seeing anything that might spoil the 3D effect. To ensure these glasses work with your TV, the TV must have either a built-in or external syncing transmitter.

The key advantage of active 3D technology is resolution. It currently provides the only way for TVs to combine 3D with the full HD resolution that’s so quickly become an expected part of our AV lives.

Panasonic Viera VT20 Series 'Active' 3D TV

Active 3D screens are potentially cheaper to make than passive ones, too, for essentially they just need to be able to handle extremely fast refresh rates rather than having to be constructed differently. However, it’s already become clear that achieving fast enough refresh rates with, especially, LCD technology is not nearly as easy as it sounds.

The main downsides to active 3D technology are the potential for some viewers to experience a flickering effect; the amount of brightness active shutter glasses can take out of the picture; the relative expense of ‘active shutter’ glasses (around £100 per pair on average); the fact that the glasses are battery powered and so can run out of juice; and crosstalk noise.

Crosstalk is the appearance of double ghosting around the edges of 3D objects. It can be caused by multiple factors - including filming techniques. But what we’ve found with 3D TVs is that crosstalk seems predominantly caused by screens not being able to refresh themselves quickly enough to keep up with the super-fast frame rate 3D demands, so that a bit of the image intended for one eye sneaks into the image destined for the other.

The fact that screen response time appears to be the main cause of crosstalk in TVs has helped plasma enjoy something of a resurgence, since plasma naturally enjoys a faster response time then LCD technology.

Active 3D technology’s strongest backers at the moment are Panasonic, Samsung, JVC (on its projectors) and Sony.

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