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Wimbledon 3D: How the BBC is filming the tennis in three dimensions

Ah, Wimbledon: two weeks of athletic excellence, strawberries and weird grunting noises -- and all in 3D thanks to the BBC. CNET UK has gone behind the scenes.

Ah, Wimbledon. Rafa Nadal, Andy Murray, Sue Barker and the cream of world tennis are in SW19 for two weeks of athletic excellence, strawberries and weird grunting noises. This year there's an added dimension to the hallowed competition, as the BBC broadcasts the finals in 3D for free. CNET UK has gone behind the scenes to see how 3D is raising its game at Wimbledon.

3D is almost as old as the world-famous Wimbledon Championships, which began in 1877, so it's fitting the latest generation of tennis talent should come together with the new generation of 3D taking over our cinemas and TVs. Sony is one of the driving forces behind the current upsurge in 3D, and is responsible for much of the kit filming Wimbl3Don. Ugh, sorry about that, we won't say it again -- quick, let's move on before the marketing people get any ideas.

First service

The 3D effect is an illusion that there is depth to what you're looking at. We see depth in real life because each of our eyes sees something slightly different to the other. Our brain uses those slight difference to work out depth, giving us a sense of depth. Clever things, brains.

3D images recreate the effect of depth by making sure each eye sees something slightly different. That means filming in 3D involves filming two images that are slightly different -- but only slightly. If the two images are too different, the illusion won't work and it'll probably give you a headache, too. When 3D programmes are shown on the BBC or Sky 3D channels, the two different images appear side-by-side (SbyS), like this:

For the duration of Wimbledon, BBC HD wil broadcast with a higher horizontal resolution of 1,920 pixels, rather than the usual 1,440, to give more detail to the two images. You'll be able to watch in 3D on all platforms, including Freeview, Freesat, Sky and Virgin.

Parallax lines

So instead of a single camera pointed at the action, each 3D camera rig requires two cameras side by side, recording the action from the same vantage point but actually capturing slightly different pictures.

In most 3D rigs, the cameras aren't side by side, like our eyes; they're just too big, and the fine adjustments required wouldn't be possible. Instead, one camera is beneath the other, pointing upwards at an angled mirror like the inside of a periscope. That means the two images filmed can be moved to the tiniest distance apart without the cameras physically bashing into each other.

The point on which the two cameras are focusing, where they converge, controls what kind of 3D effect is created. You can have objects pop out in front of the screen, which is called negative parallax. You can have objects extend back into the screen as if the screen is a window you can reach through, which is called positive parallax. The BBC broadcasts offer 'perfect 3D', which replicates the experience of being sat in the stands, rubbing shoulders with royalty and spilling Pimm's on Cliff Richard.

3D love

There are five 3D rigs positioned around Centre Court, each consisting of two Sony HDC-P1 cameras on an Element Technica rig. These are smaller versions of those used to capture the World Cup, because there's less elbow room around Centre Court than there is around a football pitch. Here's the layout:

As well as the ten paired-off cameras, there's another single camera positioned higher-up for an overview of the court.

The 3D effect works better when cameras are positioned lower and capture longer shots than a 2D camera would. Longer shots give a greater sense of depth. Each shot is also held for a longer time, as quick cuts in 3D footage force your eyes to refocus constantly -- and that leads to hurty eyes.

From Centre Court to telly screen

Each 3D camera rig is fitted with a Sony HDFA-200 fibre combiner, a box developed for the Ryder Cup golf tournament that combines the 1.5GB stream from each camera, and sends both high-resolution streams down one fibre-optic cable. The stream arrives in the outside broadcast truck, in this case NEP Visions 3D trucks packed with more Sony production equipment.

In the OB truck, the two images are fed into the camera control unit, manned by a vision engineer, and then into the the Sony MPE-200 processor box. Sony calls this "the brains behind all live 3D production". It's a multi-purpose processor box that sucks up multiple high-definition feeds and transforms them in real-time into what you'll see on your screen -- and it does it with the same Cell processor as your PS3.

As well as handling the footage from the five 3D rigs, the MPE-200 processor is also taking traditional 2D footage from the camera placed higher up for an overview of the court, and turning that 2D footage into 3D.

This is where the stereographer comes in: the 3D Jedi who checks the 3D stream. The role is entirely new for this new generation of 3D. The feed is then checked by a convergence puller, another role specific to 3D production. They check the focus point of the 3D footage is consistent.

This Craver pulled his convergence once, it bloomin' hurt. We couldn't focus right for a week, either.

Game, setup and match

The 3D footage then goes via the playout engineer to the director. The resulting video is now ready to be seen by the excited audience. It's scrambled by a 3D signal encoder ready for beaming to your 3D telly, which decodes the 3D image back into two slightly different pictures, and plays them in your living room.

The 3D glasses you're wearing make sure each eye receives a different image. Each eye beams its own separate image into your brain, your brain does the maths, and bingo: it's like that tiny little Maria Sharapova is right in front of you, so close you could almost reach out and touch her. But don't try, your mates will laugh at you.

New balls, please

The men's and women's singles finals take place this weekend and will be broadcast in 3D on BBC HD. Will you be watching Wimbledon in 3D? And which players would you like to see so close you could reach out and touch them? Serve up an ace in the comments or lob us a backhand on our Facebook page.

Image credits: BBC, Leon Neal, Denver Post