Home Toys Article
- February 2005 -
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The bottom line is that there is a projection screen viewing surface and configuration designed to fit into whatever problem space you can come up with.
Today's projection screens are much more sophisticated than the old bedsheet on a clunky tripod your dad used to drag out of the closet to show Super-8 home movies. Today, families are planning an AV system as part of their standard entertainment budget. As part of this increased interest in "home theatre" systems, there are projection screen options than ever-and every one of them is much better than a bedsheet! Here are a few choices you may face.
Permanent vs. portable?
First, you need to decide whether the screen is to be permanently installed or portable.
Most home use will center around a permanent projection screen.
If it's permanent: Fixed or retractable?
When choosing a screen to install in your home, the first decision you need to make is whether it is to be fixed in place (permanently tensioned), or retractable.
Permanently tensioned screens are usually stretched onto a frame, and most have a black border to frame the image. Many use snaps for attachment; the snaps are visible on some models and hidden on others. The most attractive fixed screens use a continuous extrusion as an alternative to snaps, securing the screen more smoothly without the pull points required by snaps.
If it's retractable: Manual or motorized?
If you choose a roller-operated screen, you next need to determine how that roller should be operated. Three options are available:
A motorized screen is extremely convenient to use. It can be integrated with a master control system, or operated with its own remote or wall switch from wherever needed. Most motorized screens are hard-wired, so an electrician may be required for installation. For this reason, it's usually easier to install a motorized screen when a room is being built or renovated than to add one to a finished room. Motorized screens are more expensive than manually operated screens.
Manual spring-roller screens are common in classrooms, so they are familiar to almost everyone. They are available in sizes through about 12' x 12', but in the largest sizes a pole is usually needed to reach and operate them. This is the least expensive type of projection screen.
Crank-operated screens offer the benefits of a tab tensioning system with the lower cost and easy installation of manual operation.
Another choice: Tab-tensioned or free hanging?
Motorized screens are available with either a tab-tensioned viewing surface or a free hanging surface. Most manual screens have free-hanging viewing surfaces, with the exception of certain crank-operated manual screens which are tab-tensioned.
A third choice: Surface mounted or recessed?
Both motorized and manual projection screens are available for mounting on the wall or ceiling, or recessed in the ceiling. Ceiling-recessed installation is common for motorized screens; wall/ceiling mounting dominates the market for manually operated screens.
On the Surface
Front projection screens are available with a wide variety of viewing surfaces, designed to work in various viewing environments. Here are descriptions of some general types. Some of these viewing surface types may not be available from all projection screen manufacturers.
First, let's look at two basic ways projection screen surfaces can be made:
Textile Backed Screen Material-Textile-backed screen surfaces are usually mounted on a roller without a tensioning system. The reflective surface is laminated to a woven textile base (usually fiberglass). These surfaces are kept suitably flat without tensioning because of the stability of the material and the weight of the bottom dowel. Textile-backed surfaces are commonly used for single lens video projection, as well as for CRT video projection.
100% Vinyl Screen Material-These screen surfaces are tensioned vinyl with no backing. Available only on motorized, crank-operated and fixed screens that are equipped with a tensioning system, they are stretched perfectly flat, resulting in better picture quality. Flatness is always desirable and highly recommended for CRT video.
The following is a list of projection screen surface types based on their optical qualities. Some of these are typically made with a textile backed or 100% vinyl construction, while other types are available in both configurations.
Matt white-The standard to which all other screen surfaces are compared. A matt white surface diffuses projected light in all directions, so the image can be seen from any angle. Matt White provides accurate color rendition and superior clarity, and is recommended for use with high light output projection devices. This surface does require control of ambient light in the audience area. Matt White is available with fiberglass backing for free-hanging screens, or in 100% vinyl for tensioned screens.
Glass beaded-A glass beaded viewing surface generally consists of a fiberglass matt white substrate, to which a uniform covering of spherical glass beads has been adhered. The effect is brighter on-axis (straight ahead) viewing than matt white surfaces within a narrower viewing cone. The beads are not as smooth as a matt white surface, so there is some loss of clarity and resolution. The optics of a sphere cause the projected light to be reflected directly toward its source, so a glass beaded surface works best when the projector is mounted at or near the audience's eye level. Glass beaded surfaces cannot be cleaned, and are not recommended for use with ceiling or floor mounted projectors, both of which are commonly used is home theatres.
Acoustically transparent-Acoustically transparent screen surfaces have tiny holes to allow sound to pass through the surface, so that speakers can be located directly behind the screen and still perform well. The best acoustically transparent surfaces are similar in gain performance to standard matt white. Some acoustically transparent viewing surfaces are 100% vinyl, requiring a tensioning system. Others have fiberglass content permitting them to be used on a wide range of screen models. Most acoustically transparent screens have a slightly lower resolution than other viewing surfaces.
Moderate contrast-Some viewing surfaces are similar to matt white, with increased contrast and gain, within a narrower viewing cone. Consider a moderate-contrast surface for projectors producing 1000 ANSI lumens or less. These surfaces are generally unbacked vinyl, so they require tensioning systems, and have smooth surfaces, for good resolution. One advantage is that moderate contrast surfaces usually tolerate a slightly higher ambient light level than matt white.
Grey high contrast-Grey front projection surfaces began to grow in popularity two to three years ago, in response to the increasing availability-and affordability-of brilliant LCD and DLP projectors. Grey surfaces provide much better contrast and black reproduction than standard surfaces, with a lower gain. The grey color enhances black levels in the projected image, so the whites appear brighter. A grey viewing surface usually allows for more ambient light in the audience area than traditional surfaces. Grey viewing surfaces are available with and without fiberglass backing.
Putting it All Together
The bottom line is that there is a projection screen viewing surface and configuration designed to fit into whatever problem space you can come up with. Some home theatres even utilize rear projection, which we haven't covered here. Rear projection requires a bit more room, because the projector and a reflective mirror must be hidden in a space behind the screen. Once you've decided the type of screen configuration and surface you want, it's time to decide the size of screen, which we'll cover in the next issue.
Terry Coffey handles Media Relations and Technical Publications for Draper, Inc., a manufacturer of projection screens, lifts and mounts for projectors and flat panel displays, window shades and gymnasium equipment.