The front projection screen must moderately diffuse the light that strikes it from the projector. If the limited light is not diffused to places where it is not needed, and is instead diffused in a concentrated manner to where people are watching the images, the screen can be effective. We use the word "diffusion" because the screen's function is to diffuse this light, and this is the most important aspect of screen performance.
For example, if the screen were to have a glossy surface, or be mirrored like a metal sheet with a glossy luster, it would not function. If a mirror were to be used as a screen and an image were projected on it, no image would appear. Only the lens of the projector would appear as a dazzling light.
If you think about this in a simplified form, consider screen substitutes in your immediate surroundings - pure white drawing paper or a sheet, a white wall, a whiteboard or even a steamy mirror could serve as a screen. An image will even appear dimly on black paper, velvet cloth or a blackboard. Things that are white reflect a lot of light, while things that appear black absorb most of the light.
Now, we will explain the optical characteristics of three types of screens.
Seldom seen in our close surroundings, this type of screen has the optical features of a road sign. A road sign appears very bright in the headlights of your car. When light is projected onto the glass beads, it is the nature of light to return; in short, the maximum radiation intensity returns to the light source (projector). The screen gain (Gs) is about 1.5 to 3. Watching the image from a position near the projector is a good way to evaluate the screens' performance. Note that it will appear darker than a white matte screen beyond a 20 - 30 ° angle to the right and left of the projector's optical axis. By increasing the angle of incidence with the projector, this screen reduces the deleterious rays that return to your viewing position.
This is the type you would have if you had chosen silver paper or a fogged mirror as a screen. This type provides the maximum radiation intensity, much like the way a mirror reflects light. Screen gain and diffusibility are reciprocal. If diffusion of the rays is insufficient, a higher value of screen gain can be obtained, but hot spots tend to occur. When the projector and viewer are far apart, and the projector is set as if projecting on a mirror, this type of screen is a good choice. This screen has a wide-ranging screen gain (Gs) of 1.5 to 10. When using such a screen, be aware that the higher the gain, the narrower the viewing angle. To ensure good usage of this screen, consider the screen to be like a mirror and position the projector so that it projects into the center. This is the only type with which the efficiency gain can be further increased by forming the screen into a curved surface that collects light like a concave mirror. A high gain screen is unsuitable for viewing delicate images or for extended use. It is used strictly for confirming still images in a bright environment. This screen's weak point is the uneven intensity that results when the flatness is disturbed. Therefore, it is not advisable to make a large size screen by joining this material. For this reason, reflective type screens are better when they have greater flatness by means of a frame stakeout structure or glued panel structure. If the structure can be mounted at an angle, the maximum radiation intensity can be directed to the intended direction.
If you were to choose drawing paper for a screen, it would be like this type. This type of screen has subtle characteristics without polarized diffusion. For this reason, theoretical screen gain (Gs) is 1 in all directions, but in reality it exhibits a gain of nearly 0.9. The screen gain (Gs) is the brightness and efficiency in a specified viewing direction. You can obtain a wonderful image by creating the best possible projection environment by avoiding the intrusion of outside light and by controlling lighting and reflected light inside the room. However, if a white board is selected for the screen, the projector's light source will appear as a bright spot in the center of the projected image. This is called a hot spot caused by insufficient light diffusion. Light diffusion is one of the most important functions of a screen.
This is a typical compact type of screen. The unit is fixed to the ceiling or upper wall and is pulled down when needed. Before making a selection, look for a smooth screen pull-down mechanism and a secure stop. Some models have a mechanism that softens the shock when fully retracting. Select a screen surface that does not produce V-shaped wrinkles from both upper edges or wrinkles and sags after long use. Electrically powered models are also available.
Several types are available, including a type on a tripod stand and a type with a screen case on a floor stand, among others. One point to consider when selecting a screen is the stability of the mounting. Also consider whether the stand parts are out of the way when in use. Moreover, select a screen that does not produce V-shaped wrinkles from both upper edges or inverted V-shaped wrinkles from the center section.
This type of screen is designed for portability. In other countries, it is used for larger screen sizes. Convenience and style are important selection points, but before purchasing, check the installation surface and storage conditions, since this type requires a supporting mechanism on the screen side.
With this type, the mechanism that forms a surface involves pulling the screen sheet taught around a circular frame with string or springs. This type is not suitable for portability or storage, but you can always maintain a flat surface. In particular, this function allows the screen to be completely withdrawn by tilting it, while the flatness of the reflective type is maintained. Various screens can be used for the plane of the pasted type. We recommend this be used as a reference screen.
This screen is integrated into furniture. It is used as a front-projection screen. It is especially useful in your home or office when you aren't using the screen and you find that it gets in the way. Because this screen is effectively built into the piece of furniture, such problems are avoided. Some of these screens can be raised or lowered by remote control, adding a performance effect.
Recent LCD projectors, DLP projectors and the like offer adequate brightness with ample radiation intensity. You may not consider it necessary to purchase a high-gain screen unless you need to read characters or view graphics in a very bright environment. To use the expressive capability of 3-tube projector to the maximum, subtle reflectance properties are essential. For this reason, shades and curtains are required to control secondary reflections, and a dedicated wall and room are required for the fixtures. Although its screen gain is low, a white matte type with a wide viewing angle would be a wise choice. Be aware that this may generate color shifts or fading of peripheral radiation intensity (quite noticeable when the projector focus distance is short) with beaded, silver and pearl type screens. These problems are proportional to screen gain, so selection of a lower-gain screen can solve these problems.
To summarize "Choosing a Screen the Smart Way," you may choose white matte or consider a lower gain model of each type after considering the latest projectors with their high radiation intensity and shorter focal point. It is very expensive to increase the radiation intensity of the projector if greater image brightness is required. If you choose a screen one size smaller (80 inches instead of 100 inches), you can almost double the brightness. As a larger image is projected, the brightness decreases to inverse proportion to the area. Choose a better image according to the usage environment by balancing the screen size against the brightness. Tuning the projection environment after installation is very important to obtaining a good image. The projector environment you create can make or break the screen's special features. You should comprehend the screen's special features and enjoy the excellent image by providing an environment that ensures the screen is used efficiently.
