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IMAX Laser - A closer look at the technology

"Stop me if I get too technical..."

by Steve Withers Oct 25, 2015


  • Cinema may be over 100 years old but there have never been more technological developments than in the last decade. One example is the introduction of laser projection, which IMAX recently demonstrated at The Empire in London.
    Whilst at this demonstration we had a chance to sit down with Brian Bonnick who is Chief Technical Officer at IMAX and find out more. It was Brian who originally championed the development of IMAX DMR (Digital Re-Mastering) technology, a proprietary system that was designed to digitally re-master Hollywood blockbusters into IMAX’s format. He also headed the development of the IMAX MPX theatre system, designed to enable commercial multiplex operators to more easily enter into the IMAX business by retrofitting an existing multiplex auditorium, as well as the company’s transition to digital projection and the creation of its new digital auto calibrating sound system. However most recently, he has spearheaded the development of the new IMAX Laser projection and sound systems, so who better to explain the new technology in more detail.

    Brian, do you think your new laser projection technology now exceeds what the current standards are capable of and will Hollywood have to catch up?

    Well Hollywood has been going through a period of transition with regards to 4K now for a while. It’s a slow up-take because you have to capture at a higher resolution so there’s the camera component, you have to do all your post in 4K so there’s that and then there’s the display side. In our case we’re actually doing more than 4K the way we’ve designed the dual-projector system but on the camera side you actually don’t have true 4K yet. We’re working with Arri right now to customise an IMAX version of the Arri 65 to create an IMAX differentiated product from the current capture component unless of course you’re actually shooting on film. So it’s all happening, it just takes time to progress. There’s the whole HDR (High Dynamic Range) stuff going on too, so there’s a lot that’s come through in the last couple of years. If you look at the transition from actual film, we’re 40 years in film and from our very first film projector through to our last, all the iterations of changes in design could be listed on two hands but our xenon projector, never mind laser, has undergone a number of changes in the last 7 years. The digital age is just forcing very, very quick changes in both the technology of the software through to the hardware side.

    You mentioned HDR, how would that work in IMAX laser projection?

    Well 22 fL would be the peak but any digital projector will not produce the same level of brightness that you can get in the new TVs. So in terms of projected HDR it’s may be better said in terms of expanded dynamic range but you’re also dealing with other parameters such as the size of the screen that also has an impact and changes things. In our case we’ve focused on something called intra-frame contrast versus sequential contrast and sequential is the one that, up until today, more or less everyone has made a reference to and you've seen the ridiculous claims made for projectors and TVs with 1 million to one or a billion to one! That’s nothing more than the difference from black to white but you don’t watch footage that way, there is no footage really aside from a credit perhaps where you have those two extremes. Stop me if I get too technical here but that gives you about 3% of the luminance scale at the low end. So that’s where that has merit but then if you take the brightness in the room and the light is bouncing off the walls, that drastically reduces that sequential contrast. In our application what we learned a few years ago is that you must have sequential contrast in order to get intra-frame contrast, it’s a prerequisite, but the intra-frame doesn’t come just because you have sequential. The intra-frame contrast was the one that we found our filmmakers were responding to and that’s where you’ve got a scene full of mid-tones and darks and whites and the whites aren't bleeding on a frame basis together. That’s where the big difference happens and that is what we have been finding is really contributing to HDR in a cinema environment. They’re very different beasts when you look at it in terms of a home environment compared to a cinema, you can’t really compare apples to apples.

    In the presentation you mentioned that the laser projector was capable of reaching Rec.2020, could you just expand on that?

    Well as far as Rec.2020 goes, to be truthful no projector manufacturer offering a product today is dead on Rec.2020 but, having said that, everyone is so close that we’re just splitting hairs so the answer is yes. We mentioned in the demonstration that we’ve been working with Disney on a Rec.2020 version of The Jungle Book, which is essentially a by-product of us using lasers. So it’s like we’ve been using lasers to do these other things but now we have the potential to do something else. However there is a lot of work associated with that in the post-production process and there will be a learning process involved. It’s also a very creative tool so I suspect we’re going to find some movies that come out where a filmmaker goes crazy and says they’ll saturate everything and there will be another one who is smart and says there are certain scenes where the wider colour space will help to tell the story. I think that colour space, just like HDR and high frame rate, are tools that the filmmaker has to learn how to use and use them appropriately and that just takes time and experience to happen.

    You mentioned Arri earlier, why did IMAX choose to partner with them rather than say RED or Sony?

    We did a great deal of analysis and the the Arri 65, in our opinion right now, is by far the best digital camera on the market place. Also in terms of the enhancements that we want to do to it, which I can’t talk about right now, it lends itself to those thanks to an open architecture. The other cameras in my personal opinion are a little more marketing hype than they are pure quality of image capture. So we did technical analysis of all the manufacturers and Arri was the company we chose to partner with and modify.

    Do you think the industry is moving quickly enough when something like The Walk was shot on the RED Dragon in 6K but finished in post-production at 2K?

    Well for a start the Dragon isn’t a true 6K camera, so you need to think about what the true resolution is. When you literally get down to the size of the pixels, as they start going up in perceived resolution you start to get more noise. I don’t want to down-play the RED but each manufacturer has pros and cons to their product and I’ll just leave it at that but we’ve picked the partner that we felt had the best technology.

    In terms of whether the industry is moving quickly enough, if you’re in a typical cinema there’s a thing called eye-limiting resolution. So if you’re sitting at the back of a normal theatre, most people won’t be able to distinguish between a 2K and a 4K presentation. Their eyes just won’t be able perceive that level of accuracy at that distance. IMAX is obviously a bit different and in our case there is merit to having higher resolution. There’s also something else. You can capture at a higher resolution but still display at 2K and this is what we do. So we capture at the highest possible resolution or scan at the highest resolution, so we might scan at 6K or 8K, even though our xenon digital projector is 2K resolution, and it’s a concept called 'over-sampling'. What that typically means is that if you have more data that you’re stating with, your output product will be better, even though it doesn’t have the same resolution. You essentially have more accurate information is another way to look at it. So when everyone else switched over to 4K for xenon digital projection we didn’t and we did that most cognitively.

    4K digital projectors have a sequential contrast that is at best around 1,800:1 and sometimes only 1,600:1. And whilst we can still enhance that, we could get the contrast up substantially on a 2K projector because at the time we were buying other people’s projectors and basically ‘hot-rodding’ them, tearing them apart and rebuilding them whilst adding our own ‘secret sauce’ to them. When we sat with filmmakers and we looked at content in an IMAX theatre, it was the contrast that was important. People often get caught up a lot on specs but it’s the sum of how it all works together that’s important and you can’t just compare one variable to another. So we made a cognitive decision to stay at 2K resolution because the contrast gains actually overpowered any perceived resolution gain.

    That is still the case with our 2K xenon digital projector but in laser because of our completely redesigned core and optics, we were able to find ways to increase the contrast ratio of a 4K digital projector. First of all we have dual 4K chips, although we also did that with our 2K projectors that had dual 2K chips which allowed us to double the resolution for both 2D and 3D. We have a device we call an image enhancer that is like a super computer that's equivalent to 100 desk-top computers and it takes our content, whether it was captured in 2K or 4K we always convert to 4K, and then this device manipulates the data going to the left and right projector for 2D and 3D. So the two images are slightly superimposed at an angle to one another to enhance the resolution and we end up getting a higher perceived resolution on screen.

    How is the new IMAX sound system superior to a competing immersive audio format like Dolby Atmos?

    Dolby Atmos, DTS:X and Auro-3D or whatever Barco end up calling their system, are all really good systems when compared to what they used to have in terms of emanating a sound from a specific location within the theatre but to be blunt that’s where it stops. So for their systems they go into a multiplex and they don’t know how the room has been acoustically treated, which is important because the room has just as much impact on the sound as the equipment and the initial recording. So they don’t have control over that, in addition the cinema chain is buying its speakers, amplifiers and other components from different suppliers and they’re generic off-the-shelf, so they can only be optimised so much. The other problem with the object-orientated system is that every theatre may have a different number of loudspeakers and so they very smartly designed their systems where they’ll mix the objects to handle up to 64 channels to support these objects but recognising that one theatre might have 12 speakers throughout and one might have 64. So the decoder in the theatre has to figure out how its going to break those objects up. So in a sense it’s making creative decisions, although it isn’t actually being creative, it’s just doing the maths but it’s redistributing objects which is differentiating one theatre sound from another.

    However in our case because we use this technology called PPS - Proportional Point Source - sound meaning every speaker is a custom design, we can create what is called a phantom sound image to make a sound emanate from between two or three loud speakers triangulated, whereas theirs can’t, which is why we have always used discrete channels. So the benefit of that is that with 12 channels we can emanate a sound from anywhere in the theatre. The other important area that nobody else has figured out and gotten on to is managing the theatres and the reverberations in the theatre, the equipment that you’re installing and the tuning of it. If you put 64 speakers in a theatre a layperson will go that must be fantastic but if you think about how you tune all of this and how you make every loud speaker sound identical to all the others - it isn't that easy. So that if a sound is moving around, how do you make sure that every speaker is playing it back with the same cadence and tonality. If there is a slight variation your ears are very susceptible to picking that up. So we’ve spent a great deal of money on the tuning. We’re using a computer to equalise tens of thousands of points when we tune a room, so we’re addressing every single component. They have a better system in conventional theatres than ever before, so hats off to them, but the rest of the equation they haven’t yet tackled.


    Given all these factors, how do IMAX maintain their quality control?

    We have a very involved training programme for operators, both internet training and on-site training when we do installations but more importantly than that, when we used film-based projectors the projectionist were really experts at their craft, it really was a specific skill set. With digital projectors today you fundamentally push a start button and the human element has been removed and they train high-school students to run them. Recognising that fact, by using the industrial camera at the rear of the theatre we’re setting it up every single day. There's an auto-focus lens rather than requiring a projectionist to do it properly, which should involve the use a pair of binoculars to check the focus and you only have to be out a tiny bit and you’ve lost that very important sharpness. So our decision was let’s not rely on that person, let’s use this camera which can zoom in at extreme accuracy whilst controlling the lens focus. So every morning when the system powers up we will adjust focus.

    We will also adjust the brightness of both projectors because one of the biggest problems with xenon lamps is their brightness degrading, they don’t hold their brightness. We designed our system so that the lamps would maintain this 60% higher brightness over other systems for the life of the lamp. So as the lamp gets to about 90% usage, the screen that the operator uses comes up with a message that says ‘change your lamp’, at 95% our Network Operations Centre gets a message from the projector informing them that the bulb hasn’t been changed and we will call the client and tell them to change the lamp. Normally that takes care of it but I’ve had the very odd occasion where it gets elevated to me and I’ll authorise one of our guys to go out and change the lamp at our cost and we’ll worry about who is paying later on.

    So it’s all this automation that we’ve put in where the feedback system is a closed loop, it’s not just some piece of equipment telling the operator that the brightness is falling, it actually makes the adjustment in the projector and if it can’t do it then we get involved. So we’ve pulled the human element out of it, but it’s a good question because it’s a critical part of the movie. If you come in right after I’ve tuned it, you get a great image but what about if you come in a month from now? Our reputation is on the line so this is something we implemented three years ago, I still consider it in its infancy but we want to get to the point where are system is preventing problems rather than reacting to them. 92% of all field problems are resolved through our NOC either on the phone with the client or via one of our guys logging in remotely and changing parameters.


    Do you think any film can benefit from an IMAX presentation?

    Well we do very few comedies or dramas because if you’re going to pay a premium as a consumer you want an experience that you’re not going to get elsewhere and what IMAX does to enhance that experience. So with an action, adventure, sci-fi or fantasy movie it tends to take the customer somewhere where they can’t go otherwise. Whereas a drama or comedy, we’re not going to add that much to it, so I think there are certain genres that we do extremely well and I think our documentaries are a really good example. But typically IMAX movies tend to be in those big screen categories of action, adventure, sci-fi and fantasy. The Walk may be a little bit different because it is a drama at its core but it also has some fantastic 3D and special effects associated with it. You feel like you’re up there on the wire with him, which is what IMAX is all about.

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