The cause, consequences and avoidance of glare
A common cause of decreased visual comfort and reduced visual performance is dazzling light. Glare is very annoying and impairs the recognition of contrasts and affects our well-being in the workplace – the result is headaches, tiredness, inattentiveness, and an increase in the error rate, especially on long working days.
Types of glare
Glare can occur in two ways, by direct glare or by reflected glare. The big difference lies in the cause.
Direct glare
The cause of direct glare lies in excessively high luminance levels and not glare-free lights. Glare is caused, for example, by unsuitable or incorrectly installed light, unshielded lamps or by unhindered daylight shining through a window in the direct field of vision.
Reflected glare
The cause of reflected glare is reflections on shiny surfaces or metallic workpieces caused by high luminance levels and excessive luminance differences, e.g. by an incorrect workplace position or incorrect arrangement of lights.
Besides, we can also make a distinction concerning the effect or consequence of glare on people. Two keywords are “physiological glare” and “psychological glare”.
Physiological glare
The glare directly reduces vision, e.g. when looking into a light source.
Psychological glare
In the case of psychological glare, the perception of disturbances is essential. In contrast to physiological glow, however, this type does not significantly impair vision. Often we perceive psychological glare as disturbing only in the long run. Therefore, we usually notice negative consequences such as fatigue or a reduced sense of well-being and reduced concentration with a time delay.
Glare rating
To evaluate glare in rooms, we use the standardised UGR method to DIN EN 12464-1. In evaluating glare according to this method, especially the size and number of the luminaire(s) in the room, their arrangement and shielding angle and the (average) luminance are crucial parameters.
For example, you can use a general diffuse light directly above the table as long as you illuminate a single workstation. In this case, the lamp can only dazzle if you tilt your head up. When there are multiple workstations in one room, the correct arrangement of lights in the room is crucial. Otherwise, other lights in the room can be disruptive.
It would be best if you also shielded lights that are too bright to prevent direct glare. For this purpose, DIN EN 12464-1 defines minimum shielding angles above specific luminance values. The minimum shielding angle describes the angle between the horizontal plane and the viewing direction at which the light-emitting components of the light sources are just visible.
When using compact fluorescent lamps with luminance levels between 20,000 and <50,000 cd / m2, the minimum shielding angle is 15 °, for example. The following table provides an overview of the specified minimum shielding angles:
| Luminance density in cd / m2 |
Minimum emission angle |
| 20.000 up to < 50.000 | 15° |
|
50.000 up to < 500.000
|
20° |
|
> 500.000
|
30° |
Glare control
You can quickly eliminate glare by using suitable workplace lights and a corresponding lighting concept!
Height-adjustable pendant luminaires or flexible articulated lamps allow the luminaire head to be adjusted to eliminate direct glare. If the luminaire head is positioned higher, you can reduce glare using suitable metal grids, panels made of plastic or a micro prismatic screen, plus additional high-tech diffusor foils.
Also, by proper placement of the lights in the room and a suitable cover, the LED modules (e.g., by an opal disk) can be eliminated reflected glare during the processing of glossy parts (e.g., in the repair and production of watches).
Let’s summarise the most important: We should avoid glare of any kind, as it affects our visual comfort and performance.
The solution is a well-thought-out lighting concept and optimally glare-free workplace lights.