10 changes to the way sport is shot for 3D TV
29th Jun 2010 | 09:18
How Sky has changed the way it shoots sport for 3D viewing
It may have missed out on the World Cup but Sky has big plans for showing sport in 3D. The satellite king will be showing live football, rugby and cricket amongst others on its 3D channel this year.
January witnessed the first live broadcasts of Premier League football matches in 3D for punters at pubs across the UK. Recently Sky launched its 3D channel, currently broadcasting a showreel of 3D highlights plus the occasional live event such as the first cricket match to be shown in 3D on 8 July between England and Bangladesh.
For living room viewers the 3D channel (no 217 on the EPG) is currently available free to top tier subscribers. You do, of course, need a new generation 3DTV, but existing Sky+ HD boxes can be upgraded via a software update.
Here's how Sky has changed the way it shoots sport for 3D viewing.
1. A technological short-cut
Sky could have taken the same Full HD approach to 3D chosen by Blu-ray but in order to work with its current Sky+ HD boxes the broadcaster chose a lower resolution side-by-side method of delivery. Using two specialised cameras to shoot 540-line images at slightly different angles, the resulting image is combined by your TV to form a single 1080i image running at 25fps, for which polarised glasses are required to view. 3D screens from Sony, Samsung, LG and Panasonic are compatible with the technology.
2. Camera positioning
Eight camera rigs (with two cameras on each) were used to film the inaugural live 3D broadcast in January of an Arsenal vs Manchester United match from the Emirates Stadium. Camera mixing, slow motion replays and overlaid graphics were handled from a purpose-built broadcast truck and the transmission was accompanied by a specially tailored commentary.
The vital factor is placing the cameras in positions that create interesting angles, not just replicating the traditional side and end-on locations used for 2D broadcasts.
Darren Long, director of operations at Sky Sports says: "If we move our cameras to the corner positions we've got a much more interesting shot than we would have face on because we're giving an angle and when you're giving an angle you create depth, you create height and create distance. That's why angles work really well in 3D."
3. Slower camera movements
A lot of training has been needed to help cameramen switch from shooting in two dimensions to three. "Within standard and high-definition the rules of following a game remain the same," explains Long.
"With 3D you completely change the rules. Number one: you don't want fast movement. You don't want the cameraman to swing the camera around, as you want to allow the person to view the content."
4. Wider fields of vision
"You're also working a lot wider. Cameramen are used to working in this 4:3 "safe graphics" zone, which is trying to keep the information into a 4:3 area within a 16:9 frame. What we've had to say is "you've got the whole picture area." This is 3D and our graphics are suited to the whole width of the picture."
The 3D experience has traditionally been about propelling objects towards you, but this can throw up problems when filming live sporting events which are, by their very nature, unpredictable.
5. Critical framing challenges
A major challenge for 3D operators is avoiding 'edge violation', which is something suddenly poking out from the bottom or the side of the frame. This is really off-putting in 3D, because you suddenly get a large object coming in from the side, bottom or top which detracts your eye away from the information.
"We have to teach our cameramen about keeping content within the frame and making sure that a person always remains in frame and not half out and half in. It's a lot of learning," says Long.
6. Multi-tasking camera operators
A key part of the training process has been a move towards multi-tasking. According to Long, "What we're doing is making camera operators what we call "stereographers", getting them to do another job so that they learn. Stereographers are the people that sit in the truck and choose the point at which you want the convergence to happen – the point of interest in the 3D broadcast.
"You've got the cameraman who's pulling focus and pulling zoom and the convergence operator in the truck that's pulling the point of interest and setting the depth positive and negative within the frame. If it's coming out of the frame it's a negative and if it it's going back it's a positive."
7. A scientific approach to depth perception
A criticism often levelled at 3D is that it can be hard on the eyes. To counteract this, Sky's cameramen are educated in the science of depth perception and how the eye works.
"Your eyes can't zoom," continues Long. "If we're looking around at objects we cut between different objects, we're not panning and zooming, we're going from one to the other and our eyes are constantly re-focusing. What you do in 3D is ask the eye to move around the frame and adjust as you zoom in. You've got to be very careful that it's not an experience where you're telling the eye to do something that it wouldn't normally do. If you're too close to an object your eyes converge into the centre. That's a painful experience."
8. Relocating onscreen graphics
Onscreen graphics are part and parcel of televised sport, but in a 3D context there's a high risk of distracting or annoying your audience.
"It's difficult," admits Long. "What we've got to ensure is that we don't turn it into a cartoon film where we've got too much coming out of the screen and people are getting uncomfortable with changing their focal point between the graphics and the live action.
"We've been trialling things like the score line and the Sky Sports logo, which we're sitting on the screen 'plane'. Imagine there's a piece of glass on the screen, we've been sitting it as though it was on that glass. So if the picture is coming out towards you, we will put the score line slightly behind "on the glass" so it doesn't take your eye away from the action that's actually happening."
9. Creating an immersive experience
Long believes the aim of 3D sports is to deliver a more immersive experience. "With 2D we tend to force people to look at an object that the director thinks is important, like, the centre of a scrum in a rugby match. You have so much information going on in a confined space.
"With 3D you start focusing on the ref, what he's talking to that guy about or things like the billboard or the crowd, which is what you would do at a normal sporting event. It's like having a front row seat that moves around."
10. Helping the sport develop
Long proffers the intriguing possibility that 3D football could also impact the game itself. "We showed an Arsenal game to the chairmen at the Premier League and they were blown away about it. They started to think 'this would be good for training.' We could start seeing where the players were on the field in much more detail than before'. It's opened up a new world to them."