The Significant Other: The Projection Screen
A tremendous amount of research can go into deciding on a projector, but the selection of a projection screen can be just as important--not in terms of capital outlay, but in terms of the impact it can have on image quality. The wrong projection screen can make images look terrible, which, in turn, can impact the way students receive and absorb information in class. But the right one enhances the contrast, brightness, and sharpness of images and can lead to less eyestrain for the viewer.
How do you determine the best screen for the classroom, lecture hall, auditorium, or meeting room? The size, the fabric, the style, the proportion, and rear versus front come into play, as do the specifications of the projector itself. Here are some considerations.
Which mechanism to select is probably the easiest of the decisions. The choices: ceiling, wall-mount or portable, tensioned or not, and manual or electric.
Obviously, ceiling and wall mounting are permanent solutions for rooms in which projection is required routinely. Portable screens are in fashion for those facilities moving toward shared equipment that can be wheeled into rooms as needed. Mounted screens are far more secure and protected: They are harder to steal and less prone to damage since they aren't carted here and there. In addition, the mounted screen is usually retracted when not in use, so the fabric is protected as well. The retraction feature, (as opposed to fixed-frame in which the full screen remains on the wall), is more relevant to the classroom. Fixed-frame screens are more likely to be used in a lecture hall than a classroom, since the lecture hall screen isn't as exposed to traffic.
Some other important mechanical considerations include:
- Tension: A screen without tension may cost less, but the design means that the screen hangs freely and is subject to movement owing to airflow in the room. A tension mechanism keeps the screen in place.
- Retraction (electric versus manual): Electric, while more expensive, is more convenient, and it is also less hassle than trying to pull a screen to the correct angle to lock it into position.
An image that's too large for the space is hard on the eyes and strains the neck as the head turns from side to side to view information. Too small a screen means text is hard to read. The wrong size can also negatively impact viewing angles. So first, one must work with the projector to position it (or adjust the zoom) or provide the best sized-image for the particular audience size and seating arrangement.
Aspect ratio is another size consideration. A 4:3 proportion was for many years the standard for presentations, such as PowerPoint-based material. But 16:9 and 16:10 widescreen proportions are gaining in popularity with the increased use of high definition content. Some believe PowerPoint and other presentations will move to widescreen as well. So another consideration in choosing a projection screen is whether to buy 4:3 or a newer widescreen aspect ratio.
The two most common choices of screen color are white or gray. White is obviously the most common and the most versatile. Gray screens, however, can make up for a projector's shortcomings in contrast levels and can provide deeper blacks.
The screen's gain is one of the basic differences between screens. The gain is how much light reflectivity a screen delivers. Screens with higher gain deliver brighter images, and they are common in classrooms where there is ambient light to combat or in locations where lights are left on. So higher gain screens are better, right? Not necessarily. High-gain screens have drawbacks. They are more susceptible to "hot-spotting," noticeable when the center of the screen appears far brighter than the edges. High-gain screens also can result in reduced viewing angles, meaning some people seated too far to the side will have trouble seeing the images. Finally, high-gain screens may affect the appearance of the colors from different viewing angles.
The gain is a measurement found in all projection screens, but the screen material will vary greatly from manufacturer to manufacturer. Some of the basic screen materials are fine for any environment where the light can be controlled. Other screen materials may be designed for areas with high ambient light or for different projection technologies, such as DLP or LCD, and some are designed to accommodate high definition resolution and even 3D. Some screen materials are fine for data, but others are designed specifically for video. Some have glass beads embedded in the material for even greater light reflection. Some screens are flame-retardant, and some you can actually clean as needed.
Rear Versus Front Projection Screens
Rear projection technology--projecting from behind through a translucent screen--is popular for a number of reasons, including the ability of rear-projection screens to address ambient light, since they tend to deliver brighter images, and the fact that lecturers using rear-projection screens needn't worry about disrupting the image while pacing.
The downside is that rear projection usually has limited viewing angles. It can be more expensive and occupies more space in the room, since the projector resides behind the screen. New short-throw projector technologies, however, have practically eliminated that space challenge, since some models can project an 80-inch image from just inches away from the screen.
Selecting a screen is downright tricky. Unless you want to become an expert in screen technologies, you may want to ask for recommendations. A projector manufacturer should know which screen will maximize the potential for a particular model. The AV systems integrator and the screen manufacturer will too. However you do it, do the research.
Denise Harrison is a freelance writer and editor specializing in technology, specifically in audiovisual and presentation. She also works as a consultant for Second Life projects and is involved with nonprofits and education within the 3D realm. She can be reached here.