Glare Light | What is glare, forms, types, pollution, prevention
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Light is a daily necessity of our lives. Since the introduction of the light bulb in 1879. The technology of Light has greatly improved thus illuminating our night sky. However, the use of excessive light has only caused side effects. These effects include glare and light pollution which the article will cover. We will also cover the importance of visual comfort.
What is Glare?
Glare is a visual sensation caused by excessive and uncontrolled brightness in the field of view. It is produced by brightness in the visual field that is so much greater than the brightness to which the eyes can handle. Glare ends up limiting a person’s ability to distinguish details and objects. Also, sensitivity varies between people and older people are usually more sensitive to glare due to ageing characteristics of the eye.
Form of Glare?
There are two forms of glare. They are disability glare and discomfort glare.
- Disability glare is the reduction in visibility caused by intense light sources in the field of view. How it works is that it causes a loss of visibility from stray light being scattered within the optical system of the eye. This results in a uniform brightness/luminous veil being drawn over the retina. This veil reduces the apparent contrast in the visual scene to impair visibility.
- Discomfort glare is the discomfort of annoyance or pain induced by overly bright source. Discomfort glare also refers to as “psychological glare” as a physiological test cant measure it. Thus, discomfort glare measure and evaluate exclusively based on the individual. The main physical parameters that determine discomfort glare are the brightness of glare source and background, size of the glare and position of the source.
Types of glare
Disability glare and discomfort glare can be caused by two types of glare, they are direct and indirect glare.
Direct glare is the result of high brightness from a light source in the field of vision. For example, the sun in front of a person’s eye is direct glare. Whereas indirect glare is the result of light that is reflected in the eye. For example, light from the sun being reflected from a surface to a person field of view is known as indirect glare.
Glare light pollution
Light pollution is the excessive use of artificial outdoor lighting. Reasons for light pollution include glare light, skyglow, clutter and light trespass. As mentioned earlier, glare depending on the intensity can result in light pollution altering the colour and contrast of the nighttime sky. It also disrupts the circadian rhythm, thus affecting the environment, energy resources, wildlife and humans too. Circadian rhythm is a natural physiological process of living beings. For us, humans it helps regulate our brain and cycle between sleepiness and alertness. It works by receiving information from our eyes to know when is day and night.
Negative effects of light pollution
- Environmental – The international Dark-sky association states that 12 million tonnes of carbon dioxide are released into the atmosphere due to artificial light. Carbon dioxide is a driving force for global warming. 12 million tonnes of CO2 is a lot, it will take about 702 million trees to absorb all the CO2 released by artificial light.
- Wildlife – For example in North America, 100 million birds die by crashing into illuminated buildings annually.
- Humans – We are regulated by circadian rhythms. These rhythms respond to light and dark. Melatonin a hormone that regulates the sleep cycle is affected by light pollution. This hormone is activated through darkness thus light pollution only reduces the hormone’s deficiency. This results in sleeping disorders.
Also according to Mario Motta, president of the Massachusetts Medical Society states that Glare light scattering across the eye causes loss of contrast which can lead to unsafe driving.
The picture on the left shows a picture of the constellation Orion took during a dark sky while the picture on the right shows a picture of Orion taken from a city. (Picture: Flickr, jpstanley)
How to prevent and reduce glare light in the office?
- Filter and diffuse light – Direct light causes the most glare. Diffuse light with lampshades and use curtains on windows to reduce glare.
- Work surfaces – Ensure work surfaces are dull instead of shiny as reflected light reflects more off shiny surfaces which results in indirect glare.
- Wear polarized lenses
- Anti-glare coatings
- Adjust light level to necessary
- Install adjustable light so workers can adjust the light level
- Use automatic brightness on computers and phones
- Desk arrangement – For example instead of having to face a window, adjust the desk perpendicular to the window to reduce glare.
Importance of visual comfort in the office
Visual comfort is a subjective reaction to the quantity and quality of light within any space at any given time. The concept of visual comfort depends on our ability to control light levels around us. Changes in light level can cause stress, comfort, fatigue and many more. There are three aspects of visual comfort.
The physical aspect of visual comfort: It depends on views of outside space (connected to nature), light quality, brightness and absence of glare. Numerous scientific studies have shown that working in an office with a view compared to a windowless office have more positive impacts on mood and satisfaction.
The psychological aspect of visual comfort: Studies have shown that light influences our bodies and mind. For example, as mentioned above about the circadian rhythms and how light levels can affect a person’s sleeping habit. Thus, showing how light can influence our health and well being.
The socio-psychological aspect of visual comfort: Everyone has a different background and culture that shapes the way we appreciate the light and visual environments. Thus, we all have our preferences when it comes to the light’s colours.
Light is something we should greatly appreciate and has improved our lives. However, it is important that we learn how to efficiently use light. As the side effects such as glare and light pollution will only impact negatively on our environment.