Da-Lite Screen Company and Joe Kane Productions have entered into a strategic partnership to design, develop and manufacture High Definition (HD) projection screens for the Home Theater and Film Production markets. Da-Lite is the leading worldwide manufacturer of projection screens and Joe Kane Productions (JKP) is a leading HD expert and consultant.
“The advent of newer and more technology driven HD digital projectors feature a new generation of optics that make most traditional projection screens obsolete,” stated Joe Kane, President of Joe Kane Productions. One such projector is the 1080p single chip Samsung SP-A900B DLP projector, which was developed with the assistance of JKP. It set a new reference in home theater projector excellence. “Once we had developed the projector,” continued Kane, “we realized that traditional projection screens were not able to display the incredible detail or uniformity of the image it was capable of producing. We turned to Da-Lite for a solution that would let the professional broadcast community as well as the Home Theater viewer experience the exceptional performance of the video projector.”
The result of the collaboration between Da-Lite and Joe Kane Productions is the JKP endorsed Affinity Series projection screens from Da-Lite. Da-Lite had introduced three screens in the Affinity series. They include a 0.6 gain screen, a 0.9 gain screen and a 1.1 gain screen. Each has a characteristic of low directivity providing a wide angle of view, flat spectral response and no surface irregularities to add noise to the image. Each screen type produces an image with a remarkable flat field in luminance and color with an incredibly quiet picture. Noise isn’t being added by the screen surface. The three types of screens are part of the Affinity family of screens that offer options in screens based on projector horse power and image size, all providing a reference image quality.
“When Joe explained the difficulties his new projector had utilizing traditional projection screens, we challenged our chemists and engineers to develop new materials that would deliver the best HD digital image in our experience,” said Blake Brubaker, Vice President of Da-Lite Sales. “With the Affinity series screens we have the first materials designed to deliver the next generation of HD digital projector images. We are extremely pleased to launch the JKP Affinity Series using these break-through projection screens.”
JKP has a history of being involved with the development of screen materials for video projection. We were often requesting screen characteristics that ran contrary to the conventional wisdom and practices. We wanted low gain screens when projector manufacturers were demanding higher gain screens. We wanted a neutral color, where all colors of light would be reflected equally. This was at a time when conventional screens were noticeably blue and or blue-green. We even saw a movement towards red in screen color, which was said to compensate for the lack of red in some projector lamps.
Once we got involved with lamp based projector we needed options in shades of gray screens. Their properties assisted us in obtaining better black levels from smaller images, or sort of large images being driven with oversized projectors. We eventually reached a point in projector detail capability where there was an interference pattern with the grain structure of the surface of the screen and the pixel structure of the projector. This called for yet another look at the way screens were being made.
All of this was being done while some consumers were still asking, “What do you mean we can’t just project the image on the wall?” Picking the right screen is a critical part of what you see from a video projector. As the resolution capability of projectors continues to increase, it becomes easy to illustrate why the screen is such a critical part of your home theater system.
We feel some of the trends currently being promoted in screen technology go against consumers’ best interest. If you haven’t guessed curved screens head our list. From the point of view of a high quality image, curved screens should have died a permanent death with the passing of Kloss Nova-beam projectors. But, somehow, what’s old in new again, as we forget why we abandoned the idea in the first place. The new reason for needing curved screens is just as old as when they first appeared. It is a fix for something wrong in the projection path.
It sort of reminds of us of other industry issues, as in shooting motion picture films. There is never enough time to shoot it right, but always enough time to re-shoot and or fix it in post. Some projector manufacturers have gone back to specifying curved screens to apply a patch to the poor lenses they are using for an anamorphic stretch to a 2.35:1 image. The industry has once again sold the consumer a bill of goods, hiding the fact that they messed up. The irony is that if you either buy a better lens so the curved screen isn’t necessary or drop the stretch idea altogether, you’ll end up with a better image.
Before going into our current discovery of better resolution in the projector requiring a better surface quality in the screen, there is another perspective on the history of screen technology we find fascinating. When you get into the science of what it takes to properly reflect light we are often surprised that in 100 plus years of manufacturing screens we are still learning what it takes to make them better. Who would have thought in this age the screen could be a limiting factor in image quality?
As we’ve already indicated, some of the difficulty in developing truly good screen technology is wrapped up in a similar problem found in producing truly good display devices.
It’s sometimes difficult to take an objective look at any individual product when we seem to be placing a priority on form over function. In the case of the screen we are often asking it to compensate for poorly designed rooms and or faults in projectors. Form gets sold without ever explaining the many consequences of using the screen as a patch from something else going wrong in the system. This is the reason we feel the reality of what the screen should be doing is overlooked. “We’ll just fix the system problems in the screen” … without ever understanding the compromises being made by not fixing it at the source of the problem.
As TV set manufacturers have always sold their sets by promoting how different they are, we’ve drifted far enough away from the requirements of the video communications system that the idea of making it function properly has all but been lost on manufacturers and consumers alike. (We illustrate this point in our introduction to high definition video in DVE HD Basics.)
JKP has always had the goal of specifying screen materials that will be neutral in reflecting the capabilities of the projector. We’ve been careful in limiting what we ask of a screen in compensating for performance issues in other parts of the system. Gray screens are an example of where we are asking the screen to compensate for a problem in lamp based projectors, so even we are looking carefully at where the screen can help the overall system performance. Done right, gray screens can be a good thing.
So what has us motivated to keep moving forward in screen technology?
With the help of the Da-Lite Screen Company, we’ve shown a new screen material that solves the important issues left open, prior to our involvement with a true 1080p resolution from projectors. The new material has allowed us to show an image quality so good that everyone seeing it was certain we had a new projector. What demonstration participants saw was a far better contrast, more detail and far better uniformity over the entire image area. All three of these improvements, each in itself being large, have surprised most home theater installers. I’m not sure any of us, including me, were prepared for what fixing the remaining problems with screens was going to do to the picture quality. It didn’t seem possible the screen could make such a large difference.
What we were able to determine was that in all of our prior demonstrations of the projector we had never had a screen that would allow us to show the audience what the projector was doing. After seeing the projector on the new Da-Lite Affinity screen we even sent a note back to the projector manufacturer telling them the lens was much better than we had originally thought. It was clearly capable of delivering a detail level we had never seen before.
In trying to describe how and or why the screen properties have made such a difference we’ve found that we have to find a new way to describe the parameters of the screen. The new way of defining screen characteristics would have to involve the challenges being presented by pixel based high resolution projectors. Home theater dealers, installers and consumers need to know more about what it takes to get a good image at home. The largest improvement in image quality would be seen from the best projectors using this screen.
The primary reason for wanting to change how screens are described is that the angle of reflectivity of light from the screen was widened in this application. Light is more evenly reflected in every direction rather than being directed forward towards the center seat of the viewing area. Widening the angle of reflectivity got us a serious improvement in the uniformity of the image. Every part of the image looked good. There weren’t any hot spots in the screen.
Normally this screen parameter is described in terms of ‘gain’, but the number for gain in this screen is similar to many other screens that don’t perform nearly as well. We realized the numbering system used to describe gain was misleading in presenting the screen’s real characteristics. At the same time we need to specify this number when determining its fit with any projector.
The second part of needing to change the way screens are described involves the improvement in the surface itself. It is so smooth that there is almost no visibility of the screen in the image. In the past the granularity of the screen created an interference pattern with the pixilated image from the projector. Now when you put up a flat field is looks as if each pixel were backlit. All you see is what the projector is putting on the screen, not anything of the screen itself.
The combination of the wide angle of dispersion and the screen becoming ‘invisible’ in the image gave us something we hadn’t expected, a serious improvement in the adjacent area contrast of the image. What we determined was that since there was essentially no visibility of hot spotting every area of the picture looked better in contrast. Since there were no surface elements of the screen scattering light to adjacent areas of the screen local transitions in the picture had a better contrast. Taken together the image looks as if it has a seriously better contrast. None of this could be measured or specified in the normal on-off contrast measurements provided by projector manufacturers.
All of this together produced a significant surprise in understanding the real capability of the projector. Prior to this screen series we never actually knew what the projector was capable of doing.
In asking for these screens we realized that increasing the angle of reflectivity would require tighter control of the viewing environment, but felt this would be easily accomplished in a professional viewing condition. When we saw that actual improvement in image quality we decided the screen should be made available to consumers as well as the professional market. Besides, it supported our position in the industry that if you get things right you’ll see the best image quality you could get from the system. We think consumers should be able to take advantage of what is required in post production.
The bottom line in image quality is that you won’t get good quality by making a lot of compromises. The primary reason for high gain screens has been to compensate for poor viewing environments. Those screens have been adding significant compromises in the image quality, so the image will still be far less that it could be. Basically, if you don’t control the environment you won’t get a good image. If you do control the environment then you can make good use of the Affinity series screen to deliver the best image quality we’ve seen.
Getting back to how to describe these screens we’re going to offer suggestions based on what we’ve learned in our presentations of the Da-Lite Affinity series. We’ll start with screen gain since we’ve already introduced it as an important part of what is new about this screen. From there we’ll move to the surface quality of the screen and pick up screen shape along the way.
Prior to gray screens the gain has been fairly easy to understand. A gain of 1.0 suggested light was being reflected equally in every direction. Anything higher than 1.0 suggested the surface of the screen was reflecting light forward towards the audience. There was a significant fall off in the amount of light that could be seen at the left, right, top, or bottom of the screen. About 14 years ago we determined that a gain above 1.3 caused hot spots in the images at the proper viewing distance for high definition images.
Some screen manufacturers were quick to point out that the visibility of these hot spots was partially dependent on how far away the projector is from the screen. They are right in that the 1.3 value was determined using CRT projectors that had rather short throws. The projector was placed at about 1.3 to 1.5 times the width of the screen back away from the screen. The actual number, 1.3 to 1.5, was projector lens dependent. Some had a ‘short’ throw, 1.3, while others were able to provide a more uniform picture by placing the projector slightly further back from the screen, 1.5 times the width of the screen.
Along came lamp based projection technology and lenses that would allow the throw distance to be much longer. The projector we’re using can be as far away as 2.2 times the width of the screen. In theory the screen gain could be higher and you still wouldn’t see the hot spots. A higher gain screen would provide audience members seated directly in front of the screen with more light than they would see from a low gain screen. So what could be bad about that?
Higher gain screens introduce hot spots into the picture. The visibility of those hot spots is partially determined by the viewing distance, as well as the projector distance. The projector being further away from the screen can reduce that visibility but it won’t make it go away. Then there is the problem of what one manufacturer says is a 1.3 gain may depend on how they are measuring it.
Up to this point screen gain has been measured based on the reflectivity of a magnesium carbonate surface. If light from the screen is higher than that reflected from a magnesium carbonate surface it is said to have gain. Obviously, if the screen were to actually have true gain it would have to have to be a light amplifier. In reality it gets its gain by reflecting light directly back at the viewer instead of reflecting it equally in every direction, as does the magnesium carbonate surface.
We measure gain by shining a light in the direction of the screen and measuring what comes back in the direction of the light source. We can go further and measure the amount of light that comes off the screen at various angles. Ideally, with a screen with a gain of 1.0 the light should be equal at all angles from head on to the screen to almost all the way out to the edge of the screen. Light should also be equal in the horizontal and vertical directions away from the center.
What you should also see, depending on the capability of the projector, is a uniform field of light over the entire surface of the screen with a gain of 1.0. In our describing a screen with gain we see this uniformity compromised. There are hot spots and those hot spots move, depending on your viewing position. Someone on the left side of the screen will see it as being brighter than the right side. Someone on the right side will see it as being brighter than the left side.
It’s easy to see hot spotting in high gain screens. If we pick most rear screen projector sets you know if you are up close to the screen you’ll be able to see a significant hot spot, usually a wedge of bright light. As you back away from the screen you’ll see the bright part of the picture getting larger. As you continue to move back the bright spot will eventually fill the screen. The point at which the screen appears to be equally bright over the entire surface of the image might be said to be the focal point of the screen. Unfortunately that distance away from the screen is much too far back for you to see any of the detail in a high definition image.
In order to take advantage of all of the resolution in an HD mage you have to sit rather close to it, probably about 1.4 times the width of the image for a true 1080p source. Back in the days of 1.5 focal length lenses on CRT projectors we determined that gain number was 1.3. Using screens of that era we don’t see enough of a difference in the image from projectors at a 2.2 focal length to revise our numbers. We’ve stayed with the 1.3 gain number as being as highest you should go in screen gain for an HD image.
Along come gray screens with gains of 0.8 to 1.1. Theoretically, if you don’t see hot spots in a 1.3 gain screen you shouldn’t see any hot spotting in something well under a 1.3 gain. But that isn’t what you see. There is significant hot spotting in these ‘low gain’ screens. So what happened? What happened is that many gray screens have really high amounts of directivity towards the front. If you equate screen gain to light fall of from center to edge, these screens have a really high gain even though the number given for their gain are around one. How is this possible?
Their gain, when compared to a magnesium carbonate surface, may be around 1.0 because the gray material pulls the light down, then it comes back up to nearly one by being directed forward. But when you look at the screen it will be a shade of gray compared to the magnesium carbonate surface.
Okay, why isn’t directing the light forward a good idea? Who sits at the edge of the screen anyway? That has certainly been the conventional wisdom. Besides, high gain screens provide isolation for the centrally located viewer from ambient light coming in from the sides of the screen, the bad viewing environment we were telling you about. The problem is, just as you see hot spots when sitting close to a rear screen set, there are hot spots in high gain front screen at the proper viewing distance for HD images. The entire image won’t be uniform in intensity. Worse yet, if you move around the position of the hot spot in the screen will travel with you. No two members of the audience will see the same image.
We had another surprise in the way gain was being measured. It turns out the lamp source being used to measure gain is incandescent, red-orange in color. It doesn’t cover the entire color spectrum you would expect from a video or film projector. The lack of covering the entire light spectrum of film or video has introduced errors in the numbers being quoted for gain. The numbers are not reliable when trying to figure out the screen size and type for a given projector.
We’ve seen cases where the numbers we measure for screen gain are significantly higher than the numbers provided by the manufacturer because we make our measurements from the light of the projector instead of an incandescent lamp.
The overall numbers used for gain should be derived using a lamp source that represents film or video projection. Since in today’s world they are based on UHP or Xenon lamps, one of those lamps would be a better choice of a light source when measuring gain.
Is there a potential down side to screens that reflect light equally in all directions? The answer is yes. Here’s the justification often used for selecting higher gain screens. These screens will give the primary viewer (in the money seat) more isolation from light coming into the screen from the sides than can be obtained from a low gain screen. Light coming into the screen from the sides will be more visible to the viewer on a low gain screen.
So what light could possibly be coming in from the sides of the screen? In an ideal viewing environment there would be no light coming into the screen from anywhere but the projector. It’s when you start making compromises in the environment of the screen that you get into trouble with light coming in from the sides. Obviously if you have any room lighting hitting the screen it will compromise image quality. The next source of light falling back into the screen comes from reflections of screen light off side walls, the ceiling or floors. For those of you who have mirrors on the back wall of your home theater, take a cue from vampire movies and cover them up while watching movies.
A low gain screen, something at or below the characteristics of our original 1.3 gain screen, is required for a uniform image for a viewer of HD content. The reflectivity of the environment around that screen has always had to be minimized in order for that screen to work. As the reflectivity of the screen becomes more uniform than our 1.3 gain screen the environment around the screen becomes a bit more critical.
Assemble the environment properly when using one of the new Da-Lite Affinity screens and you’ll be rewarded with some of the finest images you’ve ever seen from a projector.
While on the topic of room light isolation, gray screens have an advantage over white screens for reducing the visibility of unwanted light hitting the screen. Just as the gray material is used to pull down the ambient light level of the projector it will also darken any unwanted light hitting the screen. Knowing that we use gray screens to pull down the ambient light of a projector, and that such screens give us some ambient light rejection qualities, we suggest the use of gray screens from the Da-Lite Affinity series where they can be made to work. These are important points covered in our dealer training for both the projector and screens.
We briefly mentioned that many screens available today have a blue or blue green tint to them, reflecting those particular colors more than the red end of the visible spectrum. There were and continue to be all sorts of excuses for doing this. The original reason was to compensate for the yellowing of screens with age, and exposure to smoke. Then there is the belief that a blue white is ‘better’ than a neutral white, something not lost on laundry detergent and toothpaste manufacturers. The green side of tinting came from the idea of human beings seeing better at green, therefore the reflectivity of green should be higher. Of course that reasoning is as ill-advised as saying we should pre-emphasize the mid portion of the audio spectrum because we hear better in that frequency range.
Many of the compromises made in screens, as in spectral response and light fall off towards the edges of the screen, have been made in the name of improving the capability of the projector and or providing some immunity to less than good environmental conditions. What is missing in that logic is the characteristic of the screen is a fixed solution to a variable problem.
While on the topic of asking the screen to ‘fix’ something wrong in the source, we’d like to briefly mention curved screens. While this has little to do with the screens we’ve developed with Da-Lite, it is part of the larger story of miss using screen technology to compensate for errors elsewhere in the system.
The original ideal behind curved screens for video projection back in the days of the Kloss Nova-beam projector was the screen had to be curved to get a high enough gain to provide a useable amount of light for the viewer. I was even part of looking at curved screens for light output from video projectors from the early 1970’s to the late 1980’s. At the time it seemed to be the only way to get a useable amount of light from a video projector. The screen gain was often in the order of 15. You couldn’t even move your head without seeing a significant change in light output or color. The surface of these screens was often silver coated to increase reflectivity. Just touching the screen left a permanent reminder of having done so.
Everything old is new again for those who forget the past and why we found it necessary to dump curved screens in the first place. There back! Even more frightening is silver screens have made a brief appearance for 3D images. The silver surface was said to be necessary to preserve the different polarizations of the left and right eye images. Da-Lite has proven that is no longer the case. But even their innovation may be short lived if we determine the 3D projection systems should be fully compatible with the best of 2D imaging, the Affinity series screens.
We dropped out of supporting video projectors, with their requirement of curved screens. Along came the Sony 1270 being shown on flat screens. Granted the screen gain was 2 or more, but they were flat screens. JKP determined if you could deal with a smaller image we could reduce the gain to 1.3 and produce a far better image than anyone ever thought possible from a video projector. If you wanted a brighter image, just add another projector. We were heavily involved in stacking projectors.
Curved screen made a come back in someone’s quest to make 2.35:1 letterboxed images fill the screen. The 2.35:1 letterboxed image is stretched vertically to fit the 1.78 aspect ratio of many solid state projectors. It is then stretched horizontally back to 2.35:1 using an anamorphic lens in front of the projector’s lens. Some of the early, inexpensive lenses used to stretch the image out to 2.35:1 had focus problems at the edges. The original solution was not to fix the lens, but to curve the screen to compensate for the focus errors. It became a fixed solution for a variable problem. It also became a ‘new’ trend for those who forgot way we did away with curved screens in the first place.
What we are again seeing is significant distortion in image geometry and unlike the analog days of CRT displays, they aren’t easily fixed in solid state projectors. The curved screen only helped the lens focus problem but did not fix it. The irony of adding the lens in front of the projector is that it killed the focus capability of the projector. On a ten foot wide image the depth of focus on my projector is at least two feet. The additional lenses dropping that focus to less than zero, the outside edges of the image on a flat screen went out of focus. The screen had to be curved to keep the edges of the image in focus. The curved screen was then being sold in applications where it wasn’t needed. It was the ‘new’ trend. Even leaving out the geometry distortion added to the image, there is the audio distortion of the curved screen added to the room acoustics.
Oh, by the way, if you are tempted to use a separate lens in front of your projector to get a 2.35:1 image, there are lenses available to do that without having to curve the screen to keep the image in focus.
We are suggesting the screen be made to do the best job it can in image quality and the projector and environment be fixed as necessary to take their part in delivering a high quality image. For both audio and visual considerations the screen needs to be flat and have reflectivity essentially equal in all directions.
The other improvement that has come in the Da-Lite Affinity series screen is in the surface itself. There is essentially no visibility of the surface of the screen in the image. This means that local areas of the surface have to be good as well as being uniform over the entire surface of the screen. What we get from this screen is a far greater ability to display fine resolution, the screen surface doesn’t interfere with the detail. It also helps when there are large light differences in that detail, as in showing the fabric of a fine tweed jacket. Areas from the light part of the tweed don’t spill into the dark parts of the pattern.
Where do these screens fall in helping make any projector look better? In a good viewing environment the uniformity of ever image will improve when using this series of screens. They will also better reflect the detail capability of the projector. That said we are sad to report that when it comes to image resolution, not all projectors are created equal. Some do a better job with image quality than others and the better projectors will be made to look even better with these screens. Some projectors, and dare we go all of the way back to some of the standard definition CRT devices, don’t have the resolution that could take advantage of what these screens can reflect. It’s part of the reason we haven’t objected to other screens in the past. Their surface was far above the capability of the projector so it wasn’t as much as a factor in the image.
There is one advantage to the surface quality you’ll see from these screens, no matter what projector is used, and that’s a uniformity of in the entire image. In short these screens are going to provide the greatest advantage to the best projectors available while delivering an improvement to any projector.
As much as JKP has been pushing for these changes in screen materials, we were truly blown away by how important they were, and how much we needed them. Everyone knowing our image capability from past shows has been surprised by how much better our image look on this new screen. The advantages the screen offers are truly worthy of the JKP endorsement.
Joe: Kane Productions is located at
Joe Kane Productions
12526 Otsego Street
Valley Village, CA 91607