Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC

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Offline Peter CINERAMAX

After a year getting no for an answer and the commitment of Christie to deliver Blu-ray window Dolby Cinema HDRcontent, plus HDR 10 and Dolby Vision UHD BD correctly profiled alternative content on the Dolby Cinema system we have managed to convince Christie which in association with Dolby will grant license to a select number of our private Cinema customers. This is huge news for some of you here that want HDR on dci projectors that is not just the 6-8fstop HDR-10 possible next year on Barco platforms, but 12-15 HDR UHD BD Dolby Vision, and the all mighty 15-22 F-stop Dolby Cinema tour de force mother of all HDR's.

Donald when are you going to give us a review of this magnificent setup in your back yard?
Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC

From ARS Technica
Earlier in the year, our own Sebastian Anthony had the opportunity to experience the new "IMAX with laser" cinema in Leicester Square, and it didn't disappoint. Not to be outdone, Dolby Laboratories invited Ars UK to the new JT cinema with Dolby Cinema in Hilversum, the broadcasting capital of the Netherlands.

Middle-aged Ars readers may remember Dolby from the Dolby B noise reduction system used with cassette tapes. Younger Ars readers are probably more familiar with Dolby through Dolby Digital, the codec used to encode most digital audio on DVDs as well as TV broadcasts and Blu-ray discs. (Dolby Digital started out as a way to add digital surround sound to film, where the digital information is encoded on the unused space between the perforations of the 35mm film, where it can be read optically.)

The latest Dolby audio technology in cinemas is Dolby Atmos, which supports a few more audio tracks than older systems—128 of them, in fact. However, Dolby Atmos improves upon previous surround sound technologies not by simply adding more channels. Instead, it allows sounds to be dynamically placed in a 3D space. This is used to great effect when noisy objects fly over the audience; it sounds very realistic. To allow for these effects, the JT cinema in Hilversum has no fewer than 60 speakers on the walls and the ceiling of its Dolby Cinema-equipped auditorium. Dolby Atmos is currently installed in several thousand cinemas worldwide and films such as Spectre and the new Star Wars are available with a Dolby Atmos mix (in compatible cinemas).

Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC
Dolby Vision projector at 14 (left) and 31 (right) foot-lamberts (48 / 106 nits).

But Dolby Atmos surround sound is only the beginning. Actually, things begin before we even enter the auditorium: a dark corridor filled with atmospheric sounds featuring an illuminated Dolby logo at the end put us in a receptive mood as we enter. The seats are large and comfortable as usual in modern cinemas. Less common is the fact that the entire auditorium is very dark or black. This avoids distractions caused by light from the screen reflecting off of the surroundings. I'm not sure how they did it, but Dolby even managed to leave out the illuminated emergency exit signs above the doors close to the screen.

A representative from Dolby Labs explained the Dolby Atmos and Dolby Vision features that together make up Dolby Cinema. Like IMAX-with-laser, Dolby Vision uses lasers as light sources instead of the usual high-intensity discharge bulb. This allows the projection to be much brighter, and the contrast level to be much higher, than with normal DLP.

To illustrate this, one projector was used to project a white circle at the 14 foot-lamberts (fL) or 48 nits illumination level that the Society of Motion Picture and Television Engineers (SMPTE) has traditionally recommended. In the analogue days, few cinemas actually reached this level, and current digital 3D projection systems certainly don't. Then the cinema switched the projector over to Dolby Vision mode, increasing the brightness to 31 fL (106 nits) and increasing the contrast ratio to 1,000,000:1. In the image above those two circles are shown side-by-side, both photos taken with the same camera settings. In person, the effect is more dramatic.

Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC
Inside Out projected in Dolby Vision (photographed using the Adobe RGB 1998 colour space)

Finally, we were treated to several demos of the Dolby Vision system, including clips from Tomorrowland and Inside Out. In the Tomorrowland clip, the protagonist moves through a number of scenes in a world that's mostly lit by bright sunlight, but sometimes she disappears into a dark building or tunnel for a few moments. The projection system had absolutely no problem with this, showing detail in shadows even though other parts of the frame were sunlit. However, as Sebastian noted in his review of IMAX-with-laser, it's hard to draw definitive conclusions without seeing different systems side-by-side—perhaps it's just that the director of photography in these examples is really good at his job.

Inside Out is a computer-generated animated movie, and as such is free from the mundane limitations that reality imposes. The clip we got to see was one where the animated world took on a blacklight/fluorescent look with impossibly strong saturated colours, a vision that couldn't be realised using film—or by digital technologies that are trying to match film.

Time for some colour theory

We all know that the eye has cells sensitive to red, green, and blue. So all colours are made up of different levels of those R, G, and B primary colours. The CIE chromaticity diagram (below) shows how this works; pick any three colours on the diagram, and you can get all of the intermediate colours that are inside the triangle between the chosen primary colours by mixing them at various levels.

Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC
CIE chart with sRGB gamut.

The triangle shown in the image represents the sRGB / BT.709 colour space. BT.709 is the standard for HDTV and sRGB has been targeted in the computer industry and consumer digital cameras since the 1990s. However, only relatively recently have LCD computer monitors been able to display the entire sRGB colour space. Or exceed it, in the case of Apple's latest iMacs, which support the DCI-P3 colour space, (not?) coincidentally the colour space used for current digital cinema distribution.

Ideally, an RGB display device would use monochromatic primaries (R, G, and B primary colours) to create as wide a colour gamut as possible. Monochromatic light is light of a single wavelength and is perceived as the most saturated. In the CIE diagram, the rounded edge represents monochromatic colours from red (long wavelengths) to blue/violet (short wavelengths).

Cinemas, however, traditionally use enormous xenon bulbs to produce projection light. These xenon arc lights produce visible light of all wavelengths. A prism and/or filters are then used to create the red, green, and blue parts of the image. The problem is that the more saturated (closer to monochromatic) the primaries need to be, the more light that doesn't match that very specific colour gets filtered out and thus the dimmer the image will be. As a result, projectors (and LCD displays) that use a white light source can't really support the widest possible colour gamut.

Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC

Lasers to keep things safe

This problem is neatly solved by using lasers rather than a xenon bulb as the light source for the projectors. Lasers by their nature generate monochromatic light, so no light needs to be filtered out, allowing for more light to reach the screen using less electricity.

Using lasers makes the whole system safer, too. Perhaps the mental image you've had so far is three huge lasers in the projection booth that are ready to cut patrons in two should something go wrong. But that's not how it works. Laser-based projectors use an illumination of small lasers that are relatively cheap and easy to replace. Which is not exactly the case for the xenon bulbs used in large projectors; these may be rated at as much as 15,000 watts and their handling requires "the use of full-body protective clothing" (i.e., a bomb suit), as they may explode due to their high internal pressure.

Bright 3D without polarisation

The lasers also allow Dolby Vision to create a better 3D experience. Most 3D cinemas project the two images for each eye using circular polarisation in opposite directions. 3D glasses then use circular polarisation filters so that only the intended image reaches each eye. However, a bit of the image intended for the other eye tends to bleed through, especially with bright objects on a dark background, such as subtitles.

Dolby Cinema: 2 laser projectors + object 3D audio = awesome/NOW AVAILBLE for HC
The notch filter on the 3D spectacles is very visible when looking at anything other than the actual cinema screen.

Dolby Vision uses a different system for 3D projection: the two projectors each use slightly different RGB primaries, and the 3D spectacles have notch filters that block the primaries used by the projector that projects the image intended for the other eye. This turned out to be very effective; I never saw any subtitle ghosting. However, I did find that the filters lose their effectiveness near the edge of the frame. This shouldn't be a problem when sitting in the back half of the theatre, but when sitting closer, the extreme edge of the screen may get a colour cast. Don't be alarmed by the apparent difference in colour between the two lenses when looking at anything other than the screen, though—the colours on the screen look the same through each eye.

Even with Dolby Vision, 3D reduces the brightness of the image, but because Dolby Vision starts at 31fL (106 nits) in 2D, it still delivers 14fL (48 nits) in 3D mode, more than most cinemas deliver in 2D. We were shown The Martian in 3D after the demos, and it was about as bright as when I saw it in 2D in a regular cinema a few weeks earlier.

Just like IMAX-with-laser, Dolby Vision is currently available at only a handful of cinemas [not true it is also available to select DCI-Central/CINERAMAX patrons] around the world (and, again like IMAX, only a small number of films have been mastered/tweaked for Dolby Vision). In Europe, the only publicly accessible Dolby Vision cinemas are JT Hilversum and JT Eindhoven; in the US there are a few more locations (which, rather excitingly, are showing the new Star Wars film in full Dolby Vision + Atmos).


Offline randyclark

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