Low tech solutions to high tech problems in AV/Multimedia

Colleges and universities that are disappointed in the performance of their audio visual equipment often look for the next step up–a brighter projector, a newer codec, a camera with more pixels, or a more expensive control system.

Minimizing Light
Classrooms that have projectors almost never use those projectors under optimal conditions. Front projection depends on projected light reflecting off of a smooth, light-colored surface. The resulting image is perceived by a viewer as the contrast between the illuminated parts of the screen and the non-illuminated parts (black). Unfortunately, any other light from the room that falls on the image area (usually from windows and lighting fixtures) also reflects off the projection surface, making the non-illuminated parts of the image brighter than they would otherwise be. The result is an image that is “washed out,” where the colors are faded and dim. This is a bad result when your institution has invested in state-of-the-art projection systems.

No matter how expensive the projector, they all function best in a darkened room. Since projectors can only project light, not darkness, any ambient light in the room decreases image contrast. This is why cinemas show movies in blackened auditoriums. Yet instruction is rarely carried out in the dark; so compromise results. Unfortunately, often the compromise is between full lighting and energy efficiency, instead of between full lighting and projector-friendly lighting.

Here are two low-cost, low-tech ways to improve image contrast and quality:

1. Use a high-contrast projection screen. Most screen manufacturers make screens with a medium-gray reflective finish, which absorbs some of the ambient light and creates a darker baseline to improve the contrast ratio between the darkest and lightest parts of the image. Manual high-contrast projection screens cost a few hundred dollars.

2. Switch the lights closest to the screen off when using the projector. This usually consists of 2-3 fluorescent fixtures in the first row of lights. Turning these lights off while leaving the rest of the room lights on cuts most of the ambient light that falls on the screen, so the image quality is maximized while the quantity of light for student note taking is maintained at a nominal level. The cost varies depending on the classroom layout and ceiling/wall materials, but typically costs one-to-three hours of an electrician’s time per classroom.

Both of these techniques are usually well-worth the cost and effort, even as retrofits based on the increased satisfaction of classroom users.

Maximizing Light
Distance education and/or videoconferencing rooms in colleges and universities often have state-of-the-art cameras, codecs, and microphone mixing systems, and often have bandwidth far in excess of most corporate videoconferencing users. What often gets overlooked is the amount of light that shines on the interactive participants. The simplest and least expensive way to upgrade a distance learning classroom’s quality is to increase the amount of light that illuminates the participants. A light meter is a low-cost ($100-$200) device that no distance education specialist should be without. A reading of 60-75 foot-candles, as measured while holding the meter’s detector vertically (facing the camera) at each seat at 42” above the floor, is optimal.

There are plenty of opinions about whether directional lighting or indirect lighting is best (and affordable), but without enough light, the apparent quality of the output of the room is diminished. One of the most striking deficiencies of distance education rooms without sufficient light is the on-camera appearance of instructors and students with darker complexions. In order to gain enough contrast to see facial details and expressions, up to 75 foot-candles can be necessary.

Typically, the least expensive way to add more light is to put in more fluorescent fixtures. Make sure that the color temperature of the tubes matches that of the existing fixtures–its more important that the new lights match the existing than they conform to a given standard. Compared to upgrading to 3-CCD cameras and a better codec, adding lighting is a simple and inexpensive upgrade for any videoconferencing or distance learning system (and if you play your cards right, it comes out of Facilities’ budget instead of the technology budget).

Wait a minute! What about those rooms where you are doing distance learning with projectors? Isn’t it contradictory to want to reduce light but also maximize it? Like most solutions in audio-visual systems, it’s a matter of compromise in which satisfactory results can be obtained for both applications if planned and designed carefully. A few minutes spent explaining your needs to your electrician or electrical designer will lead to far better performance of your projection and interactive technologies for a modest cost.

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