(6) Lighting and contrast. Often terminals end up in a place that was not
designed for a computer. The area is generally twice as bright as it ought to be for a
VDT screen. It is difficult for the eye to adapt to both the bright room and the lower light
level of the screen. To reduce this contrast, draw the shades, use lower watt bulbs, and
fewer fluorescent lights, if possible. Room illumination should be about half what it
usually is in an office. The optimum lighting would be 30 to 50 foot candles (the
equivalent of a 60-watt bulb in a small room). If these modifications aren't feasible,
consider fitting a hood over the screen to reduce outside light.
(7) Using Video Display Terminal controls. Many users forget to adjust their
VDTs. The brightness control regulates overall brightness of the screen. The screen
should be three to four times brighter than overall room illumination. The contrast
control adjusts brightness of the characters in relation to the screen. Characters should
be five to ten times brighter than the background. You should adjust the controls so that
characters are not too dim, nor so bright that they flicker.
(8) Video Display Terminal quality. You will experience less VDT fatigue if
you are working at a good quality screen. A flickering screen should be avoided. On a
good unit, flickering can be eliminated by adjusting brightness. The color of the display
is another factor. Green and amber are more restful to the eyes, while red and blue
cause the most strain. Legibility of the characters is critical too. If you are working at a
five inch screen with tiny letters, your fatigue level will be high. Resolution, the
closeness of space between the dots, will also affect legibility and viewing comfort.
(9) Glare and reflections. Glare, one of the biggest problems associated
with VDTs, has two sources: glare reflected from light and glare from objects in the
background. To detect glare, sit in front of the monitor with the computer off. Whatever
you see reflected on the screen will cause glare when the machine is on. Take the time
to draw shades, close doors, move or shield lamps, and get rid of bright reflecting lights.
To determine when glare is blocked out, move a book or paper in front of the screen.
(Notice if that is too much glare that can be reflected from people or objects in the
background.) Position the VDT so that there are few objects in the background. If there
is a background object reflected on the screen, your eyes will constantly be refocusing
from the 2-foot distance of the screen to the distance of the object, that is, a bookcase,
ten feet away. An anti-glare filter will very effectively eliminate these problems. If your
VDT does not come equipped with a built-in filter, you can purchase an add-on. A tilt or
swivel feature on a VDT helps control glare. You can also improvise with books or
pads. Finally, even the color of your shirt or blouse will affect glare, with lighter colors
contributing to an increased glare problem.