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The year of 3D
The Business Case
Skills Shortage
The Parallax view
Depth Of Field
Active or Passive
2D to 3D Conversion
Books and Apps

Mastering 3D: The next dimension is closer than you think

This is what a beamsplitter rig looks like from the front: As you can see, the inter-axial distance between the centres of the Fujinon lenses is less than the diameter of the lenses by David Fox

Stereoscopic 3D has had a long history of being "the next big thing", looming out of the cinema screen every decade or so. Now it's back, and this time it's closer than ever.

3D is flavour of the year in the movie industry, following the huge success of Avatar, the obstacles it presents for piracy, and the reason it gives the audience to go to the cinema instead of waiting for the DVD. It is also gaining traction in the home, with broadcasters like BSkyB, ESPN, Discovery and Canal+, launching channels this year and TV manufacturers adding 3D to their sets.

The year of 3D

"2010 really is going to be the year, if we do it properly, that 3D will take off," Chris Johns, Chief Engineer, BSkyB, told delegates at the first 3D Masters conference, held at BAFTA in London by TVB Europe magazine (June 2010).

BSkyB began its 3D service in 1,000 pubs and clubs around Britain in April, something Johns called "Alcostereoscopic – you have two pairs of glasses. You wear one and you drink from the other." According to Sky's surveys, some 70% of those who viewed the service gave it an 8, 9 or 10 out of 10, which is much better than similar surveys on HD. "When you look at 3D, it's a totally different experience."

On the 1st October 2010, Sky is launching "an appointment to view service," as there is not enough 3D content for a 24-hour channel. It is on Sky channel 217 and there won't be an extra charge for 3D, initially, but it is only available to top tier subscribers. There will be a lot of 3D TV sets available by Christmas, and analysts predict one million 3D screens in UK households in 2011 – 2.5 million Sky+HD set-top boxes can already decode 3D.

The Business Case

Johns reported one Fox executive saying to him: "I'm not making any money with HD, how the hell will I make money with 3D?"

In the first six months of 2010, 3D generated some 27% of the UK box office, from a handful of movies, partly because tickets for 3D movies can cost 40% more. During the same period, more than 5,000 3D screens opened around the world, bringing the total to 13,000, and more than 85% of the digital screens installed in 2009 were also 3D. A digital projector costs about £70,000.

"Content is driving the adoption of 3D," said Charlotte Jones, Senior Analyst (Cinema), Screen Digest. There will be about 36 3D movies released in 2010, about a third of which will be 2D to 3D conversions, with live action beginning to overtake animations. 3D is also allowing cinemas to expand into live events, such as international rugby, the World Cup, or concerts.

Of the proposed TV channels being launched, 80% will include sports content.

More than 100 different models of 3D TV set are being launched worldwide this year, although most are larger sets than people typically buy now. By 2014, Screen Digest predicts that more than 18% of European homes, and about 27% in North America, will have 3D sets.

FutureSource Consulting has found "huge interest" in watching 3D in the home (about 70%, while 45% of those surveyed in the UK, France and Germany said they would be willing to buy a new TV to watch 3D). "For a new technology of this type, the numbers are off the scale," said its principal consultant, John Bird. You would usually see fewer than 10% wanting to buy new technology like this.

Polarising views: Visitors to 3D Masters check out the visuals
Polarising views: Visitors to 3D Masters check out the visuals

This is mainly driven by early adopters moving from HD to 3D, who want larger screens. The replacement cycle for TVs is about six years, with prices dropping about 25% per year. It helps greatly that 3D can be added to a set "at a reasonably low cost", and "there is no price barrier here," he said. He predicts that 3D will quickly move down through smaller sets, although many people won't use them for 3D, in the same way that about a third of HD sets aren't being used for HD now.

There is also the prospect of real-time 2D to 3D conversion within the TV set, which may undermine any premium that 3D services can charge. "It works," said Bird. "We were surprised how good it looks," and it's not entirely negative, as it could also prime the desire for 3D.

Active glasses will allow manufacturers to add 3D to sets for relatively little, but cost consumers about $100 (about $25-30 in bulk). Polarised glasses are $2 or less, but suitable screens cost more (that premium is diminishing). However, Bird believes that it will take auto-steroscopic displays (that need no glasses) before 3D can become mainstream. This could take 3-15 years, depending on who you talk to, but "we think it will be four years, or less," because there is so much research being done on it now.

There is also research needed into how the mind perceives 3D, as some people can see it only with active glasses and others with passive glasses, while some people with visual impairments, such as tunnel vision, perceive 3D better on a screen than they do in reality, while some others will never be able to see it.

"It's not a quick process to get 3D comfortable to the viewer day-in, day-out. Bad 3D is like bad HD, people will just start to turn off," warned Johns.

Although most types of programming can work in 3D, "you can't just stick 3D on any project," and Sky will only commission in 3D if there is a good reason for it.

Skills Shortage

Producing in 3D is not easy. It took Sky five months to surmount the quality threshold it had set for what it would be happy to show in public. "You have to aim for perfection. Anything less and 3D won't take off," said Johns.

"The transition from HD to 3D is a much more significant one that from SD to HD," as it involves a new set of skills and technology, said conference chairman, John Ive, technologist and consultant, IveTech.

"It's not that much more expensive once you've made the investment," said Johns. Rigs are not cheap, but are essential. He calculates that it should be possible to shoot HD and 3D on a single production for about 10-20% extra.

He advises productions to practice as much as they can and keep it simple. Sky utilised 90% of its existing production infrastructure. The 3D cameras and 3D-equipped OB truck was the largest incremental expense. The production crew had to be re-trained to shoot 3D.

"There certainly aren't enough people who can use this gear," and we need to train more crew, added Steve Schklair, CEO, 3Ality Digital Systems.

"Creatively, to jump from HD to 3D HD is a huge jump, but technologically it's not so much. HD required a whole new infrastructure over SD, but 3D is just a bolt on, and makes more financial sense than the move to HD did," he said.

Lessons he's learned from shooting 3D, compared to 2D, are:
  • 3D has its own interest, excitement in each shot, so you don't need to cut so often.
  • Staying a bit wider works. It's important to stay consistent with the depth, especially live, or you'll give the audience a headache if the depth of an object shifts widely from one cut to the next.
  • For live broadcasting fewer camera positions are needed.
  • The story is more important than the wow factor. "3D is not going to make bad content into interesting content."
  • At the moment, many events, especially sports, are being shot by both a 2D and a 3D crew, which doesn't make economic sense, so there needs to be a single crew (but almost certainly two production areas in the OB truck). "If you shoot with a crew of trained professionals, it's not that difficult," said Schklair.

    Most of the motion artefacts have now been solved so 3D can be used for even high-speed sports like ice hockey.

    3D sports requires fast reactions for convergence pulling, but drama and light entertainment can be more subtle. For live productions, "you have to be safe. You're not going to have any mistakes going to air," said Adam Sculthorp, lead stereographer, Telegenic 3D.

    Telegenic has shot more than 200 hours of live multicamera 3D, and Sculthorp said that planning is crucial. Camera positions have to be selected differently (typically lower and closer than for 2D). Allowing camera movement works better than cutting, so to go from a wide shot to a mid shot would ideally be done on a crane.

    "It's crucial both eyes match from a colour balancing sense as well as a 3D sense," he added.

    "3D doesn't need to be big, slow and expensive," thanks to new technology and more experience, said Andy Shelley, Head of Development, Onsight, who has been involved in 22 projects in the past eight months, including Flying Monsters for Atlantic Productions (David Attenborough's first 3D project).

    However, if you add a stereographer, convergence puller and Digital Imaging Technician to a typical three-person documentary crew, you could easily bust the budget and make it impractical. Besides, there isn't enough skilled crew or equipment available, so opportunities for going 3D are limited.

    Shelley advises productions to draw up budgets for a variety of different production and post workflows, because a small change in either can make a big difference financially. "You've got to make sure you've got support when things go wrong, because they will," he added.

    The Parallax View

    "The fundamental element of 3D is Parallax. Parallax is what makes 3D," said Phil Streather, Owner, Principal Large Format, who has shot 3D for Imax, cinema and TV over the last decade.

    "One of the most dangerous myths is that the optimum distance apart [for the centres of the lenses] is 2.5 inches," (7.5cm – the typical distance the centres of a person's eyes are apart). He uses interaxial distances ranging from 5mm to 5m. It is a matter of how close the closest object is, where the furthest object is, and where you want to position the screen plane.

    Budget statement: Streather's diagram of positive and negative parallax
    Budget statement: Streather's diagram of positive and negative parallax

    This will give you Negative Parallax (where an object comes out of the screen plane – an 'outie'), and Positive Parallax (where an object recedes into the screen – an 'innie'). Television screens aren't as suitable for negative parallax as a cinema screen, simply because of size. While you could believe an elephant trunk coming out of a small screen towards you, it wouldn't work with a bull elephant (which would then be perceived as small as the screen it comes out of). So, what might work well on a big screen doesn't necessarily work on TV.

    The typical "depth budget" (the total % of screen width in the foreground and background combined) for most productions is 1-2%, whereas a genre movie or theme park attraction might go to 5-10% for extreme effects.

    Your eyes can cope with negative parallax, because they can bend in to see close images, but they can't really bend out much (no more than about a degree per eye without pain). The further back in the cinema you are, the greater the background parallax can be (to make the landscape seem even bigger), so you can have a 1% background parallax if necessary. For negative parallax, Streather has gone up to 11%. But, you have to be careful, especially with the background.

    "There can be too much 3D in the shot. There is a very real danger of throwing the baby of good 3D out with the bathwater of gimmick."

    He advises viewing anaglyph images of your 3D (in traditional red and green), as it highlights the parallax differences without the need of glasses (as shown in the photographs from one of his productions).

    This anaglyph still is 0.7% positive on the clouds and 4.2% negative on the seagull. It comes from the Merlin Entertainments' London Eye 4D Experience, written and directed by Julian Napier and produced by Phil Streather.

    This anaglyph still is 0.7% positive on the clouds and 4.2% negative on the seagull. It comes from the Merlin Entertainments' London Eye 4D Experience, written and directed by Julian Napier and produced by Phil Streather.


    If you put all the 3D behind the screen, it draws too much attention to the viewing window (the screen itself), "so you need some outie parts of the picture."

    Streather is currently producing Carmen 3D, as a multi-camera shoot (five camera positions) with the Royal Opera House. Unlike similar productions in HD, you can't shoot from the back of the hall for 3D. Instead, he is using a Steadicam on stage, plus two Technocranes and a remote dolly running across the front of the stage.

    This extreme shot from The London Eye 4D is 0.7% positive on the back of the pod but 11.3% negative on the bubble being blown. © Merlin Entertainments.

    Depth of Field

    "It's an urban myth that you can't have shallow depth of field" with 3D, said Schklair."

    "Some shots work really well with shallow depth of field, others don't. If there is a really strong subject, it can work well," added Andy Milns, Director, Inition, which recently worked with Deeble & Stone Productions on Distant Thunder, a beautiful 3D natural history documentary that made good use of depth of field.

    "Focus pulls can look jarring, if it goes against the 3D, but for action, where focus would shift naturally, it can enhance it."

    mini rig quantel
    Wall-E: A mini video rig at 3D Masters

    Can you see it now?: Demonstrating Quantel's post options

    Active or Passive

    Passive rigs (ones that are set up manually and don't have any automation) are most commonly used now, mainly because they are cheaper, although they are less robust and you sometimes get movement in the rigs that cause alignment problems. They typically use prime lenses. Active rigs can correct for the fact that no two zoom rings match precisely, but they require specialist training, said Sculthorp.

    Magicine alterna
    This is a typical passive or parallel rig: The MagiCine Alterna GV-25 is a lot less sophisticated than an active rig, and about half the cost.

    The extra creative control of an active rig "is a really good idea for documentaries, where you don't have the same sort of control in other areas. They are bigger, but that is changing," said David Wooster, partner, Can Communicate.

    Live electronic correction (basically a sophisticated DVE) is also an option – Sony's new MPE-200 stereoscopic image processor was used at the World Cup.

    "You can fix a lot of grievous errors in post. It's expensive. I do not know why you'd want to do it. But with live production you need to use motorised systems," said Schklair.

    Streetdance 3D is claimed to have been the first European production to be shot digitally in 3D. It cost £4.5 million and did exceptionally well at the UK box office, earning £2.4 million in its opening weekend. It was shot using two fully-motorised rigs – one with Red One cameras and a Steadicam unit with SI-2K cameras.

    It took 40 days to shoot (two more than budgeted – due to weather rather than 3D) and 18 weeks in post (slightly more than a similar 2D production).One of the decisions that has to be made prior to production is whether to shoot converged (which typically requires using motorised rigs) and merely sweeten the convergence in post, or to shoot parallel (which would allow using a passive rig) and do all the convergence in post.

    "You usually need to shoot converged if you go live," or use an MPE-200. "For good close ups, you need converged," said Michael Reuter, Director, The Post Republic, which worked on the movie.

      Panasonic AG-3DA1
    Panasonic AG-3DA1

    Although integrated camcorders, such as Panasonic's new AG-3DA1, have a place in production, they lack the control over the lens that is necessary for many shots – close ups require lenses that are closer together (typically in a beamsplitter or mirror rig).  There is still a need for truly lightweight, portable camcorders without limitations, said Schklair.

    "Using a beamsplitter rig can cause exposure differences, which might not be even across the frame, as well as colour imbalance," according to Richard Wilding, senior editing manager, Molinare. The facility (which is currently working on three 3D productions) has worked with FilmLight to adapt its Baselight system to correct these differences, so that it can easily match colour and exposure for both eyes.

    Using a beamsplitter loses light; so high speed filming is also a problem, because it too loses light, making high-speed 3D difficult unless it is extremely well lit.

    A beamsplitter or mirror rig: Element Technica's Neutron compact 3D model with one of the cameras pointing up to shoot what's reflected in the mirror This is what a beamsplitter rig looks like from the front: As you can see, the inter-axial distance between the centres of the Fujinon lenses is less than the diameter of the lenses
    A beamsplitter or mirror rig: Element Technica's Neutron compact 3D model with one of the cameras pointing up to shoot what's reflected in the mirror. This is what a beamsplitter rig looks like from the front: As you can see, the inter-axial distance between the centres of the Fujinon lenses is less than the diameter of the lenses.

    2D to 3D Conversion

    Converting 2D footage into 3D was a hot topic at 3D Masters. Some successful 3D movies were produced that way, such as Clash of the Titans and Alice in Wonderland, but Sky would prefer to see material originated in 3D. Johns doesn't encourage 2D to 3D conversion (especially for live use), but productions can do it if there is a valid editorial reason to do so, and Sky "will accept it on a case-by-case basis, if it's well done."

    Prime Focus did a lot of visual effects on Avatar, particularly on those shots done with a single camera (such as in tight locations or walking through doors where they couldn't easily use 3D rigs), so they had to do 2D to 3D conversion.

    "It gives you much more flexibility. It gives you much more control," said Anshul Doshi, group managing director. You can decide scene by scene, it allows you to shoot with a film camera, and it can save time on set.

    It did all of Clash of the Titans. "Because of the manpower we had in India, we were able to do it in eight weeks," although it would have been better if they had 16 or 20 weeks. "It established that a post process is possible."

    There were some 2,000 shots in the movie that had to be worked on, with all the elements having to be rotoscoped (cut out), so that the client could then interactively play around with the depth. "It's expensive compared to low-cost automatic systems from JVC and Panasonic." He didn’t mention a price, but 2D to 3D conversions can, apparently, cost about $50,000 per minute.

    Doshi believes that there are some things best shot in 3D, such as sports and concerts, but some shots might be better shot in 2D and converted. However, getting the best out of the process requires planning, so you won't get the best result if you merely add it to an existing 2D production.

    Books and Apps

    StereoGraphics Developers HandbookFor those interested in learning more about 3D production, Phil Streather recommends reading:
    - StereoGraphics Developers' Handbook (free pdf download)
    - 3D Filmmakers, by stereographer and film historian Ray Zone (www.ray3dzone.com - £22.50 Amazon)
    - 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen, by Bernard Mendiburu (Focal Press - £31 or £17.50 on Amazon).

    Sky has made its technical specification for PlanoStereocopic (3D) programme content available online and if you are thinking of shooting 3D it is well worth a read (it's fairly short).

    To help calculate parallax and separation, download:

    • 3D ST (£7.50)
    • 3D Movie Calculator (£18.50)
    • IOD calc (£30)
    • the RealD Professional Stereo3D Calculator (£180)

      All from Apple's App Store for iPhone, iPad or iPod Touch.

    There is a lot more about 3D in our blog, which is regularly updated with the latest news.

    [A version of this article was originally written for Zerb, the journal of the Guild of Television Cameramen - www.gtc.org.uk]

    David Fox July 2010

    © 2000 - 2010

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