Glare
People can carry out tasks over a wide range of
lighting levels but this can be impaired when the brightness range
within a field of view is too great or when light levels change
rapidly. This is because the eye takes time to adapt to different light
levels.
The effect of any bright artificial or natural
light source, either directly or by reflection, is to create glare and
it will cause discomfort or disable a player from performing. Glare
cannot be easily classified, other than as disability or discomfort
glare. It is complex to estimate, as it depends on light level and
location of light source.
Glare is not tolerated at all in a properly
designed sports hall. Badminton has the greatest requirement for glare
free lighting because players spend a great deal of time looking
towards the ceiling, following high level shots of a small, fast moving
shuttlecock. Glare free natural and artificial lighting is difficult to
achieve and many existing halls have given it inadequate consideration.
Glare risk can be calculated using the Glare Index
calculations found in the CIBSE Code for Interior Lighting. The glare
index calculation appears at first sight to be immensely complex and
relies on tabulated data for a particular luminaire. One such table and
worked examples of the calculation procedure are reproduced in the
above publication - Page 13. The information is generally
provided by luminaire manufacturers for a particular room, luminaire,
mounting
height, surface reflectance and luminaire
orientation. A Glare Index of 19, or less, is recommended for
sports halls.
In an artificially lit hall, glare will come from
incorrect luminaire design and layout. High-intensity discharge lamps
and other point light sources can create a problem as can poor ceiling
illuminance which creates a contrast between light sources and the
general backgrounds. Fluorescent lighting has less risk of glare due to
lower surface luminance.
Daylighting poses a greater problem when designing
to avoid glare. A clear blue sky, viewed away from the sun, poses
little risk of glare although large white clouds can have high
luminance and can be a source of glare. Eliminating direct sunlight at
all times of the day limits the problem to those periods when the high
luminance of the sky near the sun might enter.
When considering both artificial and natural
lighting there should be no direct light source above the courts. Halls
designed for badminton use fluorescent lighting aligned to the side and
parallel to the length of each court. Daylighting should follow this
consideration.
