Room Lighting; Light Fixtures - Polycom RealPresence Group Series Reference Manual

Room Design and Layout
the existing wall material, then the acoustic absorption panels are placed on the interior-room side of that.
The barrier panels will have a SABIN of 0.9, but will have an additional specification of an STC (sound
transmission coefficient) of 20. STC is a measure of the amount of reduction in loudness of sound passing
through the material. Having an STC rating of 20 means there is a factor of 10 reduction in the amount of
sound passing through that material. A high-quality conference room wall usually has an STC of 60 or
more—that is, less than 1/1,000 of the sound in the room leaks through the wall.

Room Lighting

The brightness of the lighting in a videoconference room plays an important role in determining the far-end
view of the meeting. When there are low to moderate amounts of light—20fc to 35fc (footcandles), typical
office lighting—the distance range of "in focus" objects (depth-of-field) usually is only 2' or 3' from nearest
in-focus to furthest in-focus. With bright light (70fc or more) the range of in-focus objects can more than
double. Participants at the far-end will see more people in sharp focus, and the codec will have an easier
time encoding the image.
Bright standard direct fluorescent lighting has the undesirable side effect of being harsh for the local
participants. In addition, the direct down lighting casts significant "drop shadows." The result is undue stress
among participants.
The best plan for videoconferencing is to use indirect lighting for 80 to 85 percent of the light, and evenly
distributed direct lighting for the remaining 15 to 20 percent. The indirect light will help minimize shadows
on the faces of the participants, and make the room more comfortable for viewing the far-end on the TV
monitor. The direct light can be used to create backlight separation between foreground and background
objects or surfaces.
There should be not less than 55fc and ideally as much as 75fc of light (770lux) on the faces of the
participants in the facial field as viewed by the camera in the conference space. The light should be
completely even across the field of measure or view, and of one consistent color temperature.
To best meet these requirements, indirect fluorescent lighting most often is recommended. This type of
lighting works by using the upper walls and ceiling as diffuse reflectors for the light. The usual recommended
color temperature for these is 3,000 to 3,800 degrees Kelvin. If there is a significant quantity of outdoor light
entering the room, the lamps should be more than 5,500 degrees Kelvin.

Light Fixtures

The light fixtures generally recommended for indirect lighting are available from a number of manufacturers.
They typically are three-tube, 8" oval indirect up-lights, though they may take the form of chandelier-style
pendant lights, wall sconces, cove lights or flushmounted specialized troughs. Many manufacturers work
closely with contractors and lighting designers to ensure that the correct light levels and shadow-free zones
are designed into the room, especially when used for videoconferencing. Lamps for these fixtures are
available in a variety of specified color temperatures from numerous manufacturers, including Sylvania,
General Electric and Osram/Phillips. Indirect fixtures are available in a number of different designs or
"looks," and can be purchased in configurations that will complement and not detract from the interior design
of the space.
Lighting layout recommendations and determination of the number of fixtures needed are handled either by
the architectural design firm or by submitting a complete floor plan, including reflected ceiling, walls and
furniture placement, to fixture vendors. The vendors will analyze the plans and return a finished lighting
layout to the customer, detailing the number of fixtures, placement and required wiring.
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