About Projection Screens

 
Why The Choice Of A Front Projection Screen Is So Important

Because the screen is the final element in the picture delivery system, the choice of projection screen could be the most important decision you make in your home theater design process. We have seen the quality of many home theater rooms compromised because of improper screen selection. We recommend spending some time reading up about projection screens before you choose one. We have included the names, physical addresses and web addresses of the top four screen manufacturers below to help you.

Da-Lite Screen Company offers a number of excellent educational and selection guides to consumers. Ask for their booklet, Selecting Front Projection Screens For Today's Presentation Applications ,and their educational guide Angles of View. Da-Lite Screen Company, 3100 North Detroit Street, PO Box 137, Warsaw, IN 46581. 219-267-8101.
http://www.da-lite.com/

Draper Shade and Screen has a Home Theater Products brochure that you can call for. Draper Shade and Screen Co. Inc., PO Box 425, Spiceland, IN 47385. 317-987-7999. http://www.draperinc.com/

Stewart FilmScreen has a number of guides available. Also ask for their Home Cinema brochure.Stewart FilmScreen Corporation, 1161 West Sepulveda Blvd., Torrance, CA 90502 800-762-4999. http://www.stewartfilm.com/

Vutec Corporation has a literature packet that describes all of their products. Individual screen product sheets are included that illustrate screen options available and physical mounting details.Vutec Corporation, Video Products Division, 5900 Stirling Road, Hollywood, FL 33021, 800-770-4700. http://www.vutec.com/

 

The Different Types Of Projection Screens Available

Front Projected Flat Screens: The other type of screen, and far more popular in home theaters, is the flat variety. These are very popular because they more closely resemble their counterparts in commercial theaters. (As a matter of fact, in some applications, home theater screen material is exactly the same as used in commercial theaters.)

The most common version of flat screen is the manual rolldown type. These screens operate similar to window shade. You pull them down for use and let them roll up when the show is over. They are simple to use and are inexpensive. All the major screen manufacturers offer versions of manual rolldown screens.

A popular variation of the manual rolldown screen is the motorized version. These screens are generally connected to a 120VAC power source and can be lowered and raised via a switch. Many home theater installers go a step further and wire them to a relay that automatically lowers the screen when the system is turned on.

For those who want the pizzazz of motorized operation but are unable to cut holes in the walls and run AC power around (such as those who rent), Da-Lite corporation offers a unique solution. They have a battery operated rolldown screen that is infrared controlled and is charged via the standard AC wall adapter transformer. The advantage is that you can hang this screen on the wall with a minimum of effort and lower it with a learning remote control.

The standard rolldown flat screen comes in a material that is a matte (flat) white color with a gain of one. This material has excellent projection characteristics and a wide viewing angle. For those who who want a slightly brighter picture, various manufacturers offer flat screens with higher gain materials. These partially reflective surfaces offer brighter images, but at the expense of viewing angle. In addition, you have to be careful with some of the higher gain materials because you can run into a "hot spotting" side-effect that can be very distracting. (See our illustration on the next page)

Because a natural tendency of some screen materials is to curl a bit on the edges, many of the manufacturers offer "tab-tensioned" screens. These screens sport external suspension wires that pull the screen surface taut and thus eliminates screen wrinkles and edge curl. Tab-tensioned screens are offered in electric rolldown models from all the major manufacturers. Stewart filmscreen offers a manual tab-tensioned screen for those who do not need the motorized option.

For those who don't need the flexibility of rollup screens, there is another option; stretched flat screens. The surface material of these screens is a flexible vinyl sheet that stretches tight, like a drum head, over a black anodized aluminum frame. Because they are literally stretched taut over their frames, the surfaces of these screens are ultra-flat. And because these screens are simple in construction, they are very affordable and are ideal for dedicated home theater rooms. Keep in mind that flat screens are very sensitive to light in the room, thus flat screens tend to look best in dark rooms. If you can control the room lighting, (i.e. with drapes, blinds and light dimmers) then flat screens are an excellent screen choice.

Perforated Screens: Have you ever sat at the local multiplex and tried to locate the speakers? The surround speakers are no problem, since you can usually see them hanging up on the walls, but front speakers are nowhere to be seen. Well, guess what. They are right in front of you, hidden behind the screen surface. That's right, the left, center and right channel speakers are located right behind screen surface, and in some theaters the subwoofers are behind there too.

There is a major advantage to this arrangement. When sounds emanate from one of these front stage speakers they can be localized right near their on-screen image. This one-to-one correspondence of sound and film image greatly enhances the reality of the presentation.

The way the sound from these speakers reaches the audience is through thousands of tiny holes punctured in its surface. According to Don Stewart, of Stewart Filmscreen, commercial cinema screens typically have approximately 5500 perforations per square foot. This is sufficient to allow the high frequencies from the commercial, horn-driven theater speakers to easily penetrate the screen surface and reach the audience. Interestingly enough though, this material was not good enough for home use. Don explains, " Horn drivers can drive the high frequencies through the commercial screens, but standard consumer dome tweeters cannot. We took this into account when we designed our THX Acoustically Transparent material for home theater use. It has slightly over 30,000 perforations per square foot and each is so small that sound easily travels through the material, yet cannot be seen by the audience."

So, if perforated screens are the standard in commercial theaters, why are they uncommon in home theaters? There are three reasons: and the first is cost. It is expensive to perforate thousands of holes in a sheet of vinyl. The machines to perform this process are elaborate and precision built. Second, perforated screen materials are, by nature, quite fragile. Think of these like a tear-out card in a magazine. When you want to remove the card you tear along the perforations. Get the picture? These screens require a fair amount of more care during installation. The third reason is the side effect of having lots of holes in a screen surface. Not only can sound pass through them to the audience, light projected on the screen can disappear to the other side. As a result, the gain of a perforated material is less than the gain of an unperforated one. When you are trying at all costs to increase the brightness of you home theater picture, many would argue that losing any light is unacceptable. You want your screen material to perform at maximum efficiency, which would mean no holes.

What Size Projection Screen Is Best For Your Home Theater?

It is pretty common for video enthusiasts to want the biggest screen their home theater room will physically fit but this may be a bad choice for many home theater rooms. Why? consider you have two opposing criteria when you are choosing your screen size.

You want an image large enough that your whole visual field is involved in the presentation but you don't want a picture so large that it is dim and lacks sharpness.

Conclusion: Bigger is not always better in video displays. You may want to opt for the next screen size down from your original plans. But, what size projection screen is best for your home theater? First, make sure you have enough room depth so that you can sit a minimum of 2 screen diagonals from the screen if you are using a video-grade video projector. (See the diagram above.) If you are using a line doubled data projection system then you can sit at 1.5 screen diagonals from the screen.

General rule of thumb: consider a screen in the 100" to 110" range. An image this size is huge and theater-like, but is not so large that it lacks detail. If you have a room that is really large (over 3000 cubic ft.), then consider the bigger sizes, such as 120" and up.

The diagram above illustrates the conventions used in the A/V business for measuring screens.

A = The screen size (the diagonal measurement)

B = The black leader (for extending the viewing surface)

C = The black border (frames the image and hides the overscan)

Surface Options Available For Flat Screens

The standard flat screen comes in a material that is a matte (flat) white color with a gain of one. This has excellent projection characteristics and makes a nice uniform video image but one that is rather dim..

If you want a slightly brighter picture, you can purchase flat screens with higher gain material, in some cases up to a gain of 4. These higher gain materials do make the picture brighter, but we suggest that you do not use the materials with gains over 2.0 for CRT based projectors because they have a "hot spotting" side-effect that we find very distracting (the image is brighter in the center of the screen than on the outside edges.) Gains up to 3.2 are fine for LCD based projectors.