What is glare?
A dictionary definition describes glare as “difficulty seeing in the presence of bright light such as direct or reflected sunlight, or artificial light such as car headlamps at night“, but just to complicate matters, did you know that there are different types of glare to consider? Ranging from mild discomfort to impairment in the ability to see and perform a task.
Types of glare
Discomfort glare
Discomfort glare from a light source or luminaire, where brightness is greater than the eye can adapt to, makes a task uncomfortable to perform. The degree of discomfort depends on several factors; the brightness and the size of the glare source, the position of the glare source in relation to the line of sight, and the background luminance against which the glare source is viewed.
Disability glare
Disability glare is caused by a reduction of contrast which leads to a decrease in visibility. This type of glare describes the situation when the ability to perform is adversely affected i.e. driving when the sun is low in the sky or towards a vehicle using full beam headlights. Traditionally, disability glare would be associated with incidental issues such as those described and not associated with modern lighting design practice or product technology.
How-to reduce glare
The occurrence of glare is an unwanted side effect which needs to be avoided wherever possible. With the wide use of LEDs in exterior lighting schemes, glare has become an increasingly common issue due to the small scale of LEDs as a light source, and their increased directionality.
Like with most elements associated with exterior lighting, mitigation for things like glare can and should be considered during the design stage. It is important to consider location, mounting, inclination and usage when designing a new lighting layout.
Here are some scenarios and helpful hints:
- Can glare be reduced during the design phase? Lighting design software allows for glare to be understood and specified during the design phase. Consider the use of low ‘G’ rated products or those with a low upward light output ratio. Whilst on their own the G classes do not necessarily ensure a low glare solution, they tend to reduce the risk of this occurring.
- Can glare be reduced during the installation phase? Is the design over-lighting the area? Can the effect of glare be reduced through dimming/switching when the area is not in use?
- What can be done post installation? Is a retrofit anti-glare shield available from the manufacturer? By utilising anti-glare shields, any unwanted spill lighting can be controlled and redirected.
