The next picture show

WHEN Christopher Nolan’s sci-fi blockbuster “Interstellar” opened in America in November, he insisted that cinemas equipped with traditional film projectors, rather than their digital successors, could show it two days early. Fellow director Quentin Tarantino has gone further, promising the biggest 70mm film release in two decades for his next Western, and damning digital projection as “the death of cinema as I know it”.

It would be easy to dismiss such protests as petulant nostalgia for some half-imagined golden age of celluloid. After all, over 80% of the world’s 135,000 cinema screens have converted to digital projection (nearly 95% in movie-mad America), even as global box office takings topped $35 billion for the first time in 2013. Unlike film prints which rapidly acquire scratches, pops and burn marks, digitally stored and projected films look and sound as good after 100, or 1,000, showings as they did on their premiere night.

But Mr Nolan and Mr Tarantino have a point. Digital projectors cannot match the sheer detail of a pristine 35mm print, nor its rich contrast between the deepest shadows and brightest highlights. And although a digital file itself does not degrade, the xenon arc lamps that illuminate digital projectors fade over time. They can lose half their brightness in just a few hundred hours and cost $1,500 each to replace.

Things get murkier faster if a film is projected in three dimensions. By definition, stereoscopic 3D films show a different image to viewers’ left and right eyes, thus cutting a projector’s apparent brightness in half. Polarising filters, used in most 3D cinemas, halve that again. The glasses worn by the audience take a fifth of what’s left. Pity the unlucky patron who watches a 3D film at the end of a projector’s lamp life: he might see just a tenth of the intended brightness. Little wonder, then, that 3D films have earned a reputation for dimness and causing eyestrain. Nearly three quarters of people opted for the 3D version of a film in 2008. Less than 40% do today.

A brilliant idea

One possible solution involves that cinematic staple: laser beams. Rather than being attached to a shark’s head, used to intimidate an immobilised secret agent or vaporise a rebel planet, these lasers are kept safely in the projection booth. Laser-illuminated projectors cannot only deliver brilliantly bright images, in either 2D or 3D, but also promise better contrast, more natural colours, ultra-realistic high frame rates and resolutions that might finally approach those of film.

The lasers are not fired directly at the screen, as in some planetaria, but contained entirely within a digital cinema projector. At the heart of these machines are spatial light modulator chips, usually based on digital micromirror devices. The chips, which are just a few centimetres across, contain up to 2m aluminium mirrors that can be individually controlled to reflect incident light. Each one corresponds to one pixel of resolution, and a projected image is built up by combining beams of primary red, green and blue light from three modulator chips.

In a traditional digital projector, a high-pressure xenon arc lamp illuminates the chips. Even without their tendency to fade, arc lamps are less than ideal. They generate light in all directions and over a wide range of frequencies, so a series of prisms and filters is needed to split it into red, green and blue, and to direct those beams onto the micromirrors. Arc lamps can only be made brighter by making them bigger, which makes the light harder to control. The best xenon projector lamps today typically offer around 30,000 lumens of brightness.

Illuminating the same chips with lasers eliminates many of these problems. Laser diodes are small, semiconductor devices that turn electricity directly into laser light. They generate very narrow wavelengths, so there is little excess light or heat, and last for tens of thousands of hours. Their uniform light is easy to work with.

The first commercial laser cinema projectors contain hundreds of tiny laser diodes and offer around twice the brightness (60,000 lumens) of xenon-based projectors, while consuming only about half as much electricity. However, even doubling the brightness of existing 3D systems would leave many films looking dull and gloomy. Handily, lasers also enable a more advanced type of 3D operation.

Most of today’s 3D projectors have a filter that alternates rapidly between left- and right-handed circular polarisation, synchronised to scenes shot from slightly different perspectives. The viewer, wearing spectacles with lenses of opposing polarity, sees only the correct scene in each eye and thus perceives a 3D image.

Laser-illuminated projectors have more to offer than just improved 3D

An alternative 3D system relies on the human eye being easily fooled. People often perceive colours to be identical that are in fact composed of subtly different wavelengths of light. These colours are called metamers. Metameric, or colour separation, 3D uses distinct bands of red, green and blue light to make up the scene destined for each eye. Spectacles using special colour-filtering dichroic lenses then allow only the correct image to be seen.

Extracting the six different colours necessary for metameric 3D from a xenon lamp’s broad spectrum is tricky. Like polarisation, it involves filtering out most of the useful light to keep the small portion that is needed. Lasers, on the other hand, can be tuned to emit only the wavelengths needed. This means that almost all of the light they generate ends up on the screen, helping high resolution 3D films look every bit as bright as their 2D brethren.

Laser-illuminated projectors have more to offer than just improved 3D. They can reproduce up to 60% of the colours that most people can perceive, compared with 40% for xenon projectors, and with much better contrast. They can also project films at higher rates than the traditional 24 frames per second (FPS), allowing crisper depiction of fast-moving action. Ultimately, they should pack more detail into each frame and rival the best film stock.

Laser projectors are not without problems. Early ones suffered from a phenomenon called speckle, an ugly visual effect produced by waves of the same frequency interfering with each other. Lasers are also expensive. A xenon-based projector might cost $60,000 but a first-generation laser projector can run to $500,000. Even with savings in electricity and replacement lamps, the new set-ups still cost between two and four times as much.

The switch from film to digital projection primarily benefited distributors, who no longer had to produce tens of thousands of reels of 35mm film at around $1,000 each. To boost demand, distributors and projector manufacturers offered cinema owners a subsidy. With no suggestion of a similar scheme for the much pricier upgrade to lasers, it is likely that cinemas (and customers) will have to foot the bill.

And yet a few laser systems are already being installed. In November the Cinerama cinema in Seattle unveiled the country’s first laser-illuminated projector, a dual projector made by Christie, an American manufacturer, as part of a multi-million dollar refit. Ryan Hufford, a systems engineer at Cinerama’s parent company Vulcan, would not comment on the finances, saying only: “We work for [ex-Microsoft billionaire] Paul Allen. He has charged us always to be looking for the newest, most innovative technology.”

A few other high-end cinemas with deep pockets have signed up, notably the IMAX chain, whose staple 70mm film projectors are now rather dated. But there is no sign of a mass shift to lasers. The obstacles are not purely financial. At the moment, special licences must be obtained from the Food and Drug Administration, which imposes additional requirements on staff.

Even more frustrating for cinema owners is that some of the touted benefits may not arrive for years, if at all. Larger hard drives will be needed to store the additional data that comes with higher resolutions and frame rates, for one thing. But the biggest barriers are probably not technical. “The chips will look after themselves,” says Bill Beck, a long-time proponent of laser-illuminated projection now working for Barco, a projector manufacturer. “Getting all the constituents together and agreeing standards is what takes the time.”

In 2002 Hollywood’s seven major film studios set up a joint venture called Digital Cinema Initiatives (DCI) to establish standards for everyone from film-makers to cinema proprietors. It was sluggish to get going, taking years to issue its first specification, and generally trails developments. This summer, DCI insisted that laser projectors continue to conform to existing standards, limiting improvements to resolution, colour and frame rates, while it works on updating its specifications again. Without properly encoded and encrypted movie files from the studios, even the most high-tech directors will not be able to get their work in front of an audience.

Mr Beck suspects that cinemas keen to start defraying the cost of their projectors might not be prepared to wait. Some, he believes, will go ahead. “But until Hollywood says what the colour gamut, the frame rate and the dynamic range are going to be, and then supports that with production versions of their movies, it’s just going to be technology testing.”

Hobbits ahead

Even if all the benefits of laser projection can be realised, there is no guarantee that audiences will appreciate them. The late Roger Ebert, a noted critic who worked for the Chicago Sun-Times, loathed 3D films for many artistic and practical reasons, only one of which was that they were too dim. And the reception of a subsequent innovation has, if anything, been worse. When director Peter Jackson released the first instalment of his Hobbit film trilogy in 2012, it was available at two frame rates: 24 FPS and 48 FPS. Some critics loved the high frame rate, others thought it overblown, artificial or looking as though the film was shot on cheap videotape. The only other 48 FPS releases since then have been the remaining Hobbit films, although James Cameron is said to be considering high rates for sequels to the sci-fi epic “Avatar”.

Mr Ebert once said, “Whenever Hollywood has felt threatened, it has turned to technology.” In an age of mobile devices, streaming video and infinite choice, it is easy to see the appeal of a technology, however expensive, that promises to accentuate the differences between immersive, experiential cinema and watching a film on a tablet. But if we have learned one thing about lasers from the silver screen, it is that they can be very dangerous in the wrong hands.