For nearly a quarter of a century I have been labeled as a "display guy" in the professional and home theater audio visual industries. I suppose I must plead guilty to the charge after years of teaching the Advanced Display Technology courses at Infocomm and working with display companies like Hughes-JVC, Runco, Samsung, Barco, and Brillian Technologies each of whom advanced the art of the "perfect picture" in their unique way. My "graduate studies" in the pursuit of perfection on screen, was working on the first experiments in digital cinema with Disney, Paramount, Miramax, Lucas Films and Stewart Filmscreen. They opened my eyes to the level of detail we need to approach the look and feel of the 35mm film experience.
If the pursuit of digital cinema drove the focus on picture quality over the last decade, today the home cinema industry has picked up the charge and is some notable cases goes beyond the scope of the original mandate. This is the bastion of Joe Kane's Digital Video Essentials, Ray Soneira's Display Mate, and the omni present THX stamp of approval. It appears that those of us who are manufacturers, integrators, consultants, and end users that attend the annual CEDIA Trade Show are the next best hope for seeking out the "perfect picture" that is our holy grail.
If we talk about image quality in home theaters, we cannot ignore flat panel displays with advanced plasmas up to 71", LCDs with their faster panels up to 65", and we might as well throw in LCD, DLP and LCoS thin profile retro displays in the >80" range to round out the group. The "problem" with all of these displays is that they are not big enough to engulf the viewer and replicate the true cinema experience that many feel is the be all and end all of the quest. For this reason we want to examine the highest rung on the ladder and look at front projectors and front screens that truly put the viewer in the proper perspective.
We can open up Pandora's Box relative to which display technology is "best" at another time but from my perspective there are excellent projectors out there using LCD, DLP, and LCoS as the imaging source. The bottom line is that the best of the best in each area will replicate the quality of 35mm color film. We now await the letters telling us it ain't so, but save your breath because it is finally true!
Those of you thinking ahead will know that this is only half the story and of course we are speaking of the projection screen to complete the picture. In this regard let us once again take the highest road and the true cinema experience as our guide. This path takes us to the topic of the perforated screens similar to what is used in cinemas around the world.
What we thought would be a "simple" examination of what we see and what we hear in the home cinema experience relative to perforated screens, blossomed into a project with a life of its own. In doing research for the white paper there was little information on the topic and even less of a scientific nature. The following white paper evolved into a full research project incorporating some of the best audio and video minds in the industry to help us separate marketing hype from scientific evaluation and fact. It became clear that we needed a scientific approach and metrics providing data and backup for our findings. We therefore dedicate this to the people who spent countless hours humoring us in totally dark rooms, variable ambient light conditions, and testing every screen type and speaker configuration "known to man" in the pursuit of the truth.
The Perf Screen Experience:
It seems that we thrive on the "who is best" arguments in all walks of life. There is the PC versus MAC conflict and the Ford versus Chevy versus Dodge battles that fuel the NASCAR phenomenon. In our realm of replicating the cinema experience we can look to a more profound group of metrics with which to make our decisions relative to perforated screens and perhaps in the process take some of the argument out of the "who's best" discussion. We must examine:
- Appearance of resolution
- Contrast (local and broad area)
- Brightness and light loss
- Color saturation
- Cross reflection
- Acoustic transparency in perforated screens
All of these factors must work in concert with one another to give us the image and audio transparency that we strive for on screen.
First of all let's take a look at perforated screens and what they bring to the table.
In the traditional cinema environment, perforated screens are used in conjunction with speakers mounted behind the screen surface. The primary purpose is to localize the delivery of speech and sound to an appropriate area of the image, in order to heighten the sense of involvement and believability. In recent years as more and more consumers have installed home theaters, the desire to fully replicate the cinema experience has flourished. Many believe that the experience is heightened more in a home theater environment than on the big screen due to the proximity of the audience to the screen.
With the desirability of perforated screens on the rise, the question of how to manufacture the screen with "holes" in it becomes paramount. It is easy to understand that there must be a happy medium between acoustical transparency, loss of reflected light on the screen, and the perforations on the screen surface. The magic in all of this is finding the compromise among all the elements and providing an uninterrupted viewing experience at closer distances than will ever be experienced in a traditional theater.
The viewing distance appropriate for an acoustically transparent screen is dependent upon the type of perforation, and to a lesser degree, the level of illumination. As an example, in a conventional theatre, with a luminance level of 12 Foot Lamberts (nominal), the studio industry standard Stewart Cinema Screen will have the perforations vanish at a viewing distance of 15 feet whereas the Stewart MicroPerf fabrics will vanish at a viewing distance of 12 feet. SMPTE Standard 196M calls for a luminance level of 12-22 Foot Lamberts open gate in a darkened room. Many viewers these days, are not entirely satisfied, however, with a viewing experience in a completely darkened room, and subsequently aim at a luminance level more like 25-50 Foot Lamberts, in a partially darkened room. As luminance increases, perforation or texture of the surface can become detectable at closer distances therefore viewing distance should be analyzed and the viewing area should be determined in a manner that allows the perforation to vanish.
Regarding the issue of brightness emanating from the screen surface and the desire for viewing in a dimly lit room rather than total darkness, one must consider the projector and screen in combination. In our tests some screens required a doubling of the brightness of the projector to meet the viewer's requirements! It should also be noted that some screens have no cross reflective dampening which controls the spill of light on the walls and ceilings which can further degrade the viewing experience.