Projection Screen 101

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Projector's Friend.


Aug. 22, 2008 — by .(JavaScript must be enabled to view this email address)

Projection screens are often overlooked, despite being looked at. Whether you’re looking for a motorized screen or fixed screen, gray or white, matching your projector with the right screen can improve its performance, and perhaps the performance of your entire theater.

What’s in a screen?

First and foremost, a screen reflects the light from the projector. The perfect screen would reflect all of the light from the projector, block light from the room, and create a perfectly uniform viewing surface. While some screens can do an admirable job at one or two of these, none can do all.

Some screens will focus the light more towards the seating area, but if you go too far, the center of the screen will appear brighter than the rest, and people sitting “off-axis” (as in, not directly in front of the screen) will get odd hot spots to the image. Some screens can block ambient light, but not perfectly, and these often add artifacts of their own. The goal is to find the best compromise that fits your viewing needs.

Now why wouldn’t you just want to paint your wall white? Get close to your wall, and you’ll see. No matter what kind of paint you get, you just won’t be able to make that surface perfectly smooth. At worst, you’ll see this texture when you’re watching movies. At best it can create odd reflection spots. And really, if you’ve spent several thousand on a projector, why not spend a little more for a decent screen to view it on?

The Regulars

The two most basic types of screens are drop down (retractable) and fixed. Retractable screens require more elaborate installation, but offer a huge “wow” factor as your screen drops down from its hidden cove in the ceiling. This setup also allows for a flat-screen TV to be used as a daytime display, with the screen coming down in front of it for nighttime movies. Fixed screens are, well, fixed. They come with a lightweight frame, and can just be hung on a wall or stood on simple stands (often supplied).

Screen Size

With single chip DLPs, LCDs, and the popular LCOS projectors, a 16x9 screen of 130-inches is probably the upper limit for a decently bright image. There are certainly exceptions (some can go bigger, some can’t even go that big). Best to talk with your installer to find out how large a screen the projector you have in mind can fill. Keep in mind that light decreases with screen area, so a 120-inch diagonal screen is not 20% bigger (and therefore 20% dimmer) than a 100-inch screen, but is actually 44% larger, and 44% dimmer (all else being equal).

Three chip DLP projectors are significantly brighter, and therefore can have much larger screens. You can offset some of the light lost with larger screens with a higher screen gain.

Screen Gain

Screen gain is probably the most quoted statistic. In the days of dark CRTs, this was extremely important. Now, most projectors can brightly fill most screen sizes, so high gain is less important. With a high gain screen, you can get a hot spot in the middle of the image, which can be distracting. Also, off-axis viewing is diminished. A screen with a gain of 1.2 would, in theory, be 20% brighter than a 1.0 gain screen. At least, in certain seating positions.

“Unity Gain” screens like Da-Lite’s Da-Mat, Vutec’s Matte White, Screen Research’s SolidPix, and Stewart Filmscreen’s SnoMatte 100 have a “1.0” gain, and offer wide viewing angles, with no drop off in brightness as you move off axis. As far as gain goes, you can think of these as the benchmark, and you can go brighter or darker from here.

Gray screens, like Stewart Filmscreen’s GrayHawk, Da-Lite’s High Contrast Da-Mat, Vutec’s GreyDove, Draper’s High Contrast Gray, and SI Screens’ Eclipse .85 have a darker base material that darkens the whole image. These were created in the early days of DLP and LCD projectors to lower the black level by lowering the entire amount of light coming off the screen. Since most high-end projectors have a decent enough black level, these types of screens are no longer a necessity, rather a matter of preference. In larger screen sizes, the reduction in light may become a concern.

If all your seats are fairly centralized, then screens with some gain can add that extra punch, and allow for larger screen sizes with the same projector. There are many choices available like Stewart Filmscreen’s Firehawk (reviewed here), Da Lite’s Video Spectra, and others from nearly every other projector screen manufacturer.

It is possible to get screens with a gain of 2 or more. Unless your screen is going to be exceptionally large, you still have a CRT, or have some other abnormal situation, these types of screens should be approached with caution. Nearly every projector on the market can create a wonderfully bright image (as good or better than a movie theater’s spec of 14 foot-Lamberts) on a 1.0 gain 100-inch diagonal 16x9 screen. This is plenty bright. If you’re trying to combat ambient light, a light switch would do a better job, or check out one of the specialty screens later in the article.

Screen Shapes

Every current projector designed for home use has a 16x9, or 1.78:1 aspect ratio. Unfortunately, only HDTV is this aspect ratio, and nearly all movies are between 1.85:1 and 2.35:1. One of the hottest trends in the custom market is anamorphic lenses, processing, and screen masking. What this does is stretches the 2:35 image vertically to fill the 1.78:1 chip (minus the black bars). Then an external lens stretches it back out horizontally to fill a 2.35:1 screen.

The Stewart Filmscreen CineCurve (reviewed here) and the Screen Research TheaterCurve have a built in masking system that covers the sides of the image depending on the aspect ratio. Most other companies offer masking screens.

These can be either vertical masking that drops the screen to a certain point, then covers the top to create the “wider” (or in this case less tall) image, or horizontal, that slides in to make the image narrower. Keep in mind that you are always better off getting a screen that fits the room vertically, than going wider than 1.78:1. Otherwise you’re going to get a smaller screen for some material than is necessary.

Curved screens are also a possibility, though are only really necessary for very large screen widths.

Perf or not to Perf

Next time you’re in a movie theater, look for the front speakers. If you’re in a decent theater, you’re not going to be able to see them. That is because the speakers are behind the screen. From a position standpoint, this is the perfect location. After all, the voices are coming from where the mouths are. But from an acoustic standpoint, this is less than ideal. For instance, if you hold your hand in front of your speaker’s tweeter at home, and you can readily hear the difference. Putting speakers behind a regular screen would cause the sound to bounce around behind the screen (and off your speakers) and eventually arrive at your ears all wrong.

Theaters use a perforated screen (just as it sounds, tiny holes) to remedy this. But with today’s fixed pixel projectors, this can cause a problem at home, as you don’t want the pixels of your speakers to match up with the holes in the screen (possibly causing moiré). Modern perf screens (or “acoustically transparent” screens) take this into account, so generally it shouldn’t be an issue. Examples include Screen Innovation’s Maestro 1.1 Mini-Perf, Stewart Filmscreen’s Microperf X2 and Cinemaperf, Da-Lite’s Audio Vision, and Screen Research’s ClearPix (reviewed here).

Another way to do the “perf” thing is not a perf at all. Companies like Screen Excellence, Elite, Vutec, and Screen Research have a screens that are a woven material, which is acoustically transparent like the perf screens, but with no chance of moiré artifacts.

Specialty

Sometimes you really want a projector, but you just can’t control the ambient light. Or maybe your spouse refuses to live in a cave (the nerve). Several companies make screens that block or absorb much of the ambient light that would wash out a regular screen. Planar’s Xscreen, and dnp’s Supernova, are some of the heavy hitters in this category. These are both ridged screens, and as such have less options in terms of screen sizes than most regular screens.

SI Screens Black Diamond is similar to the Supernova and Xscreen, in that it blocks a lot of the ambient light. It isn’t ridged and is a black material, so when the projector is off and the lights are on, it looks like a huge flat panel. SI claims it also increases the contrast ratio of the projector. It comes in 0.8 gain and 1.4 gain versions.

One option that will truly impress is Stewart’s StarGlas. This isn’t a screen so much as it’s an actual wall. It’s rated as safety glass, and is available up to 204-inches wide. The thought here is that you would have your projector inside where it’s nice and cozy, and you would be able to watch your movies outside on a 234-inch diagonal screen, er, wall. A version of this, called the StarLift, is smaller but can be incorporated into a cabinet or stand instead of an LCD or plasma.

Make Your Own RPTV

If you just can’t stand seeing a projector hanging from your ceiling, another option is rear-projection. Here, a projector is mounted behind the screen. Installations vary, but generally this is a more involved option. This can be used in higher ambient light conditions, and nearly all modern projectors can be set up this way. SI Screens, Vutec, Stewart, Da-Lite, and others offer several options. The latter three companies, among others, also offer mounting hardware and mirror systems for a complete package (except for the projector, of course).

Lights Out

There are plenty of screen materials, sizes, shapes, companies, and gains to fit every projector. Selecting the best one for your projector (or matching a new projector with a screen) may take a little research, but is absolutely worth the time. The same projector on two different screens can look completely and totally different, even in the same room. Match them correctly, and you’ll have the home cinema experience you’ve always wanted.

COMPANIES:
Da lite Screen Company - da-lite.com
dnp - supernovascreen.com
Draper Projection Screens – draperinc.com
Elite Screens - elitescreens.com
Planar - planarhometheater.com
Screen Excellence – screenexcellence.com
Screen Research - screenresearch.com
SI Screens (formally Screen Innovations) - SIScreens.com
Stewart Filmscreen - stewartfilmscreen.com
Vutec Screens – vutec.com



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