One computer device per person is common in offices today. Computers are revolutionizing how work gets done, as well as changing requirements placed on the workplace and its design. The most common complaints among office workers about their work environment have to do with lighting and difficulties in reading their video display terminal (VDT).

Reflections on a VDT screen which interfere with reading the screen are called "veiling" reflections. They may cause eye strain and tiredness. Or they may cause one to misread the display. Both of these result in a drop in productivity and/or quality.

These reflections are caused by relatively bright surfaces or lights which are reflected by the face of a VDT. Bright surfaces are those which have a much greater light intensity than the area surrounding them.

There are a number of ways to eliminate veiling reflections or to reduce their effects. Some are measures which an individual can take without effecting his/her neighbors. Others require changes to the building or changes which effect others.


Changes Within a Single Workstation

Adjust the VDT: Try to adjust the VDT so that the reflections disappear. This will be easier if the terminal has a tilt swivel base. Its just like adjusting a mirror so there are no bright lights or objects in view.

Swivel tilt VDT

Move the VDT: Check to see if there is another location for the VDT within the workstation. Is there a spot to place the VDT so that there would be no bright lights or surfaces behind the user if he/she were seated at the VDT? Check this by placing a mirror or piece of reflective material where the face of the screen would be located. If a better location is available, consider whether the new arrangement of the work area will be satisfactory and check to see if cables will reach and power is accessible from the new location.

Light Source: If the obscuring reflection is a light source which can be eliminated without disturbing others, then turn it off. For example, the light might be a task or under shelf light in the user's own work area.

Windows: If the light source is daylight from a window, close the window blinds or drapes. In general, VDT's should be placed at right angles to exterior windows. If the screen faces a window, there will be reflections on the screen from the exterior. If the user faces the window, there will be disturbing glare due to the brightness surrounding the VDT.

User reflection: Light clothes, a very dark background or a lighting level which is too bright may cause the user to be reflected in the screen. To get rid of the reflection, it will be necessary to eliminate the contrast between light and dark. That is, have the user try wearing darker clothes, reduce the intensity of the light shining on the worker or lighten the background.

Display type: If the VDT has reverse video (i.e. it can be switched to a light background with dark images), try this. Veiling reflections are primarily a problem when the display background is dark. With a light screen the reflections are usually less bright than the screen and are therefore not visible.


Changes Beyond a Single Workstation

If none of these suggestions reduce the veiling reflections satisfactorily, it will probably be necessary to spend some money and efforts must be escalated beyond the individual work station. The following options are listed in order of increasing expense.

Polarized filter: A polarized glare filter which is placed over the face of the VDT will reduce glare and can significantly reduce veiling reflections. These cost from $90-$200 depending on the size of the screen. They are available from computer supply stores and mail order catalogs.

Screen surface: Purchase VDT's which have a dull rather than shiny screen face. The shiny surfaces results in crisp, sharp reflections that make reading the screen more difficult than diffuse, soft reflections which occur on a dull surface.

Screen shape: Purchase VDT's with flat screens. These will reflect objects over a narrower area than a spherical (worst) or cylindrical shaped screen.

Reduce light level: Another strategy to minimize veiling reflections due to light objects within a dark setting is to reduce the average lighting level. This reduces contrast ñ and consequently veiling reflections.

In an area where the primary tasks are performed at VDT's, the lighting level can be reduced below 40 foot candles. Where it is not necessary to refer to documents or where task lighting is provided, the lighting level can be reduced to as low as 20 foot candles. Satisfactory implementation will depend on selection and arrangement of appropriate light fixtures.


General Room Lighting

Often veiling reflections are caused by bright lights in the ceiling. There are several strategies to avoid this source of reflections.

Low brightness fixtures: The more common strategy is to install low brightness fixtures. These are normally fluorescent fixtures with deep cell parabolic lenses. A two foot by four foot fixture has a lens with either 18 or 24 cells. The cells are several inches deep and have parabolic sides which give a broad distribution of light. These are much more efficient than those with acrylic lens. The fixtures usually need only three 40 watt (or 32 watt) fluorescent tubes to produce the light which is available from four 40 watt tubes in an older fixture.

Do not confuse these with fluorescent fixtures having 1/2 or 1 inch square parabolic lenses. These are low brightness fixtures but concentrate the light over a small area so that the lighting level is uneven in the space. These lenses are often used because they can replace the 1/8" thick acrylic lens in an existing fixture. However, we do not generally recommend their use.

Indirect lighting or up-lighting: This solution uses ceiling hung fixtures that direct the light up where it is reflected off the ceiling. Glare and shadows are nearly eliminated. This character of the lighting has been compared to that experienced on a cloudy day. When used with task lights which can be controlled by the user, it is considered by many to be optimum.

There are several drawbacks. One is that it requires a higher than normal ceiling. We do not recommend its use with a ceiling height lower than 10 feet. This is not available in a typical rental office building. Higher ceilings increase building cubage, and consequently increase initial cost and operating expenses. Indirect lighting draws attention to the ceiling. Therefore, it requires a high quality ceiling system and installation ñ further increasing initial costs. A 2' x 4' lay-in acoustical ceiling will definitely have an unacceptable appearance. Another drawback is that the same light level requires more total power than is needed with low brightness fixture. We used this approach successfully in the SafeCard Operations Center.

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