Spotlight on Selecting a Screen

The screen is part of a system
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Because projectors and screens interact with each other and with the environment in which they are installed, the way to determine the optimum screen for every application—and avoid issues—is to take the approach that the projector, screen, environment and content are part of a system.

Therefore, when purchasing a screen, it is important for the user to consider all the factors that contribute to screen performance, including those that are apart from the screen material itself.

SCREEN MATERIALS
Front-projection screens come in basic types. One of the first things to consider is what type of screen fabric deals best with the ambient light conditions present in the space.

Matte white materials and low-gain angular reflective fabrics are highly diffusive and provide excellent white-field uniformity across the image surface, but can wash out more easily in poor lighting conditions. Those materials therefore are best for rooms with full lighting control (i.e., lighting can be turned completely off).

Gray materials typically reject ambient light better and help deepen black levels and improve contrast. Those materials usually are appropriate in environments where some light is present.

Black materials exist for the singular purpose of providing optimal contrast. Black screens typically have very narrow viewing cones. They are also prone to noticeable image artifacts including hot spotting, color shift, solarization and striations. In addition, a far brighter (more expensive) projector is required to make the image pop.

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Stewart Filmscreen Corp.’s Stealth Trap-Door ElectriScreen Silver materials are specialty, high-gain fabrics designed to compensate for losses in image brightness and contrast from passive polarized 3D systems. Due to high-gain factors and hot spotting, they are typically not recommended for viewing high-definition or regular 2D content, or for active 3D systems.

That has changed, however, with the introduction of “Silver 5D,” an innovative material (made by my employer, Stewart Filmscreen Corp.) that can power passive, polarized 3D images and provide a quality, high-definition 2D image as well (3D + 2D = 5D).

SCREEN SIZE
The ideal screen size and format vary from application to application. Boardrooms tend to utilize a 16:9 or 16:10 format or aspect ratio, but there are still quite a few 4:3 screens going into auditoriums and large venues. Visualization rooms often utilize multiple projectors to achieve wider, more immersive aspect ratios in the area of 3.0:1. Matching the screen’s aspect ratio to that of the projector is the goal. This helps to ensure the image fills the screen area and utilizes the full brightness of the projector.

Selecting the best format for an application should begin with a review of the type of content to be shown. Screens showing heavy amounts of video may trend towards 16:9, where computer graphics may be better suited for 16:10. Screens showing largely text only should select 4:3.

In addition, the size of the screen largely is dictated by content and viewing distance. As a rule, it is recommended to maintain a ratio where the distance to the closest viewer is greater than twice the image height; and the distance to the farthest viewer is no more than six times the image height. However, if the content and projector will be showcasing higher resolutions, those rules change. To take full advantage of high-definition content, the farthest viewers should be positioned no more than four times the image height.

Dave McFarland is director of marketing for Stewart Filmscreen Corp.

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