Screen Fabric Characteristics
Gain. This is simply a measurement of reflectivity of the screen. The higher the gain number, the brighter the image will appear. The increase in gain is based on how light is reflected by the fabric. Lower gain fabrics disperse light in a wide area, while higher gain fabrics reflect more light back along the projection axis. This causes higher gain fabrics to have a narrower viewing angle. When comparing these fabrics, the gain value is relative between each fabric type. The Glass Beaded fabric, for example, has a gain of 2.5, and is therefore 2.5x brighter than the Matte White fabric with a gain of 1.0.
Viewing angle. This is a measurement of the angle at which you begin to lose picture quality. This is expressed as an angle, and is measured from the screen surface and along the projection axis. To determine the actual viewing area for the audience, the angle is measured out from the axis to all directions - left, right, up, down, and in between. This creates a "cone" of sorts. As mentioned previously, lower gain fabrics tend to have wider viewing angles. This is important for choosing fabrics for rooms where the audience is close to the screen, where the room is wide, or is wider than is length. Viewing angle is also important for ceiling-mounted projectors. See the "Projector mounting location" section below.
Seamless vs. seamed. Some fabrics are listed as "seemless". This means that the fabric is one continuous piece. When fabric sizes extend past the standard width for a fabric, two pieces must be mated together. A seam may affect the image quality, but is not normally discernable. In most cases, this is only an issue for very large screen sizes.
High contrast. Some fabrics are listed as "high contrast" fabrics. The purpose of these fabric is to increase the contrast ratio of the image (see the Definitions section for more information). This type of fabric is best for home theater use where DVD or high definition movies and television images are the primary source. The contrast is increased with the use of a gray fabric base. This then enhances the black and darker colors in the image.
High gain or High Power. High gain is a term for fabrics that are generally listed over 2.0 gain. Note that high gain is not necessarily the best for most applications, and it's not true that a higher gain means that the fabric is "better". High Power is a type of fabric offered by Da-Lite that has a gain of 2.4.
When deciding on a screen fabric for your Da-Lite screens for use in your home theater or for business presentations, there are a few criteria that should be considered.
Ambient light conditions. Ideally, you would want to have a completely dark room. In this case, you would want to choose a screen with a lower gain value. However, you may be traveling with your screen and are unable to know what the lighting conditions are for the venue, and an elevated fabric would be acceptable.
Projector output power. This is typically expressed in lumens. Higher output power projectors would require lower gain fabrics. Typically, LCD and DLP projectors would not need elevated gain fabrics, unless the ambient light conditions are such that a brighter image was necessary. Older projectors, such as CRT-type projectors, would benefit from elevated gain fabrics, such as High Power, Wide Power, or Glass Beaded.
Projector contrast ratio (2000:1 or better). Typically, projectors with a listed contrast ratio of 2000:1 or better would not need the High Contrast fabric, and would instead benefit from an elevated gain fabric. These would include:
Video Spectra 1.5 fabric (1.5 gain) for untensioned screens;
Cinema Vision (1.3 gain) for tensioned screens;
Pearlescent (1.5 gain) for tensioned screens.
Projector contrast ratio (less than 2000:1). For those projectors with lower contrast ratios, the high contrast fabrics would be a good selection, especially for home theater use. Note that lower output projectors may benefit more from elevated gain fabrics than from high contrast fabrics. High contrast fabrics would include:
High Contrast Matte White for untensioned screens, for moderate output DLP and LCD projectors;
High Contrast Cinema Vision for tensioned screens, for moderate output DLP and LCD projectors;
High Contrast Da-Mat for tensioned screens, for high-powered DLP and LCD projectors;
High Contrast Audio Vision for tensioned screens, where you wish to place center and/or left and right speakers behind the screen; similar to High Contrast Matte White;
High Contrast Cinema Perf for tensioned screens, where you wish to place center and/or left and right speakers behind the screen; similar to High Contrast Cinema Vision.
Projector mounting location. Projectors can be located in several locations - even behind the screen itself.
Front projection - ceiling mounted. In most cases, this is the ideal location for your projector. However, issues with higher gain fabrics may arrise (see below). It is recommended that a 1.5 gain or lower fabric is used for ceiling-mounted projector applications.
Front projection - table mounted. Since the light from the projector is reflected back at the source, the projection axis is not perpendicular to the screen surface, and people sitting at a "normal" distance may have issues with image quality with fabrics that have a narrow viewing angles. As such, it's recommended that the projector is mounted as close to eye-level as possible when using high gain/narrow viewing angle fabrics.
Rear projection. There are a few fabrics that are designed to be used for rear projection. These fabrics have to be tensioned, so they're not available with manual or standard electric screens. Da-Tex is a rear projection only fabric, while Dual Vision can be used as a rear or front projection applications.
Media type. Typically PowerPoint presentations would not need a high contrast fabric. But, if high definition television or DVD movies are the media of choice, higher contrast fabrics would be appropriate.
Cleaning required? Most screen fabrics are able to be cleaned, with the exception of the Glass Beaded fabric. This fabric has glass beads that are impregnated into the fabric. Rubbing or rough handling can dislodge these beads, creating dead spots and ultimately affect the image's uniformity with respect to brightness. If a high gain fabric is required, and it's possible that cleaning may be required in the future (kids, dusty location), then the High Power fabric would be a better choice (it can be cleaned). Cleaning is done with warm water and mild soap.
When you choose your fabric, be sure that they are fire retardant and mildew resistant, as all of Da-Lite fabrics are.
Projection axis. This is the axis defined by an imaginary line drawn from the projector to the surface of the screen. If the projector is mounted above the centerline of the screen fabric, then the projection axis will not be perpendicular to the screen surface.
Contrast ratio. This is a measurement of the ratio of white-to-black light within your image. The ratio is calculated by comparing the brightest color possible and the darkest color possible at the same time. The higher the ratio, the better the picture will appear (sharper, more vivid colors).
Lumens. This is a measurement of light output from a source - also known as ANSI Lumens. Projector manufacturers typically list the projector output power in lumens. The higher the lumen value, the brighter the image.