Laser projection for cinema, thinks above all of the spectators, although most do not even differentiate between digital and celluloid.
By Juan Carlos Chávez*
Once the industry-wide conversion to digital cinema is complete, and with the first digital projectors approaching the end of their useful life, exhibitors will have to consider – sooner rather than later – how and with what to replace their digital projection equipment. VMPs (distributors' aid to digitalization) are over, and the multiplication of technological options makes it increasingly complex to decide the way forward. One of those options has attracted a lot of attention lately: laser projection. Until very recently, laser projection was only available in rooms of the highest level.
It offered an image of high brightness and great color, but for most of the exhibitors its profitability was quite doubtful. Well, that is about to change, and in this article we propose to explore the reasons that will soon make RGB laser projection the most used technology to illuminate cinema screens. The time has come for our industry to refocus on the viewer experience, on the people who choose to invest the budget they spend on entertainment in watching movies in theaters.
We are in a position to affirm that the public has not benefited from the initial deployment of digital cinema as much as studios or exhibitors. In fact, most viewers did not even differentiate between digital and celluloid. Today they naturally have the possibility of opting for 3D, but the low brightness of the images and the uneven gain of the screens have created new problems in many important film markets around the world. Therefore, if we want the public to continue going to the cinemas we have to offer the best possible experience, and that starts by filling the screen with spectacular images.
A spectacular image on the screen
The answer is very simple: the brighter the better; the colors will be perceived more precise and natural, the contrast will be greater and the high resolution will reproduce the details more accurately. The big studios that defined the original DCI specifications for digital cinema projectors knew all too well. Hence, they specified precise standards for on-screen brightness, color gamut, contrast ratio, and pixel resolutions required for digital cinema equipment. Specifications that were at the height of the cutting-edge technology of those years, that is, the technology of well over a decade ago.
At that time it was known:
›› How to illuminate screens at 14 fL (although not in 3D)
›› That xenon lamps reproduced the P3 color gamut
›› That the image chips could achieve a certain ratio of contrast and resolution
So, the standards became that.
However, the exhibition industry has advanced at great speed. Today consumers can buy cheap display devices for home use, with higher resolution, better color, amazing contrast and higher HDR (high dynamic range) than that offered by most cinemas.
The younger generation is more "plugged in" to technology, and will begin to perceive the presence of these new visual aesthetics, or their absence in the event that our industry is unable to progress in parallel with the advancement of technology.
Laser phosphor projection
One of the most interesting innovations recently appeared in the projection market is the so-called Laser Phosphor (LP / LaPh) or BPP (blue laser pumped phosphorus). At first glance it seemed like a revolution, since it makes it possible to create white projection light using exclusively blue lasers, using a mature and economical laser device technology that requires considerably less cooling than other lasers, thus allowing manufacturers to produce projectors that are relatively cheap and require much less maintenance than conventional projectors, especially since there are no lamps in them to change.
Obviously, this absence of lamps also means saving on the resources dedicated to ordering, transporting, storing, replacing and eliminating materials harmful to the environment. In recent years, impressive demonstrations have been carried out and commercial products using this technology have emerged, whose power reaches 30,000 lumens.
But LaPh technology has some major drawbacks, especially in cinema. To begin with, the conversion of blue light to white entails a great waste of energy (>50%). In addition, the native color spectrum of this type of projector is usually smaller than that of the triangle Rec.709 in Figure 1, being especially deficient in the case of green and red, essential colors to achieve an image of natural appearance.
Consequently, in order to achieve minimally acceptable color performance that does not impose brightness sacrifices, Projector Engineers with LaPh are forced to make difficult decisions in the design of the yellow notch filter (YNF). In the case of LaPh technology, the YNF will waste up to 50% of the available light to meet the demanding DCI P3 specification for cinema.
Let's go back to the experience of the public
What there should be no doubt about is that lasers have the potential to drastically improve the image quality of cinema screens. But to achieve this, the industry is required to evolve towards RGB laser projectors. In these projectors the light comes from a combination of Red, Green and Blue laser light precise enough to cover and incorporate the Rec.2020 color gamut.
At the same time, having red and green lasers completely avoids the loss of conversion efficiency that we detected in LaPh projectors. In addition, just as important for cinema applications, achieving the DCI P3 color specification requires no loss of brightness from a YNF. If an RGB laser projector needs more red light, it will be enough to add more red lasers.
In fact, when it comes to converting laser light into a usable light on a cinema screen, an RGB laser system is four to five times more efficient than a LaPh projector. In conclusion, RGB laser projectors have the possibility of reaching brightness levels much higher than those achieved with LaPh projectors, while offering enormous advantages in terms of the contrast ratio achievable on the screen. RGB lasers are the only cinema lighting technology capable of delivering HDR (High Dynamic Range) on the screen.
Which leads us to an obvious question: why then bother with LaPh projectors? The short answer is that, today, red and green laser devices are still considerably more expensive than the blue lasers used in LaPh projectors.
The next generation of RGB laser projection
At the moment, the good news for the film projection industry is the existence of recent advances in the field of red and green laser technology that in a short time will change everything. The next generation of laser devices, already in operation in laboratories and in prototype RGB laser projectors, is much more efficient than the projectors that currently work in premium cinemas around the world.
But in addition, these next-generation lasers do not need to be cooled like the current ones, thus allowing a very important reduction in complexity, size, reliability and cost of the system. Very soon manufacturers will begin to introduce RGB laser projectors for cinema in conventional theaters, which will work at a cost of ownership equivalent to that of a lamp projector of the same type. Those new projectors will put a better image on the screen in terms of brightness, color and contrast ratio, with the added advantage of not needing lamp changes.
If the film industry is to survive the assault of technology and the diversity of options that consumers find in other leisure spaces, exhibitors will have to strive to offer their audiences spectacular screen experiences. The screen image is an important part of those experiences, and lasers can play a critical role in improving cinema for everyone.
However, exhibitors also need to understand that LaPh is a transient technology, suitable only for small movie theaters where projectors can operate at low brightness and with the YNF intact. As the new generation of RGB laser projectors is brought to market, manufacturers will increase their production in search of economies of scale. New projectors will soon dominate the film industry, replacing both lamp and laser phosphor technology and generating real benefits to who really matters: the public.
*Juan Carlos Chávez is director of Christie in Latin America.
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