Light Angles and Glare

Glare and Light Angles in the Workplace

The energy consumed by a lighting system is often given more consideration than the quality of light, despite the fact that proper lighting can yield a 10-25% boost in workplace productivity.  Lights can be too dim or too bright, and when they’re both – you get glare.

Glare occurs when a powerful light reflects off a surface.  Too much light entering the eye makes it difficult to focus and recognize images.

Common Effects of Glare:

Physical Risks:
•Eye damage
•Job site injuries

Physiological Effects:
•Decreased performance

Research estimates that 80-85% of our perception, learning, cognition and activities are mediated through vision.  Despite our reliance on sight, however, most workplaces do not provide optimal lighting for their designated space, and this hampers occupants’ ability to perform.  
Our visual perception is negatively impacted with the introduction of a glare source, and it can cause physical discomfort via eye fatigue, headaches, migraines, stiff necks, and musculoskeletal injuries.  Building owners and employers must balance light sources and reflective surfaces in a manner that accounts for both employee productivity and comfort.

The Science of Glare

Light enters the eye through the pupil before traveling into the lens and retina.  Optic nerves in the retina analyze the light patterns and send a message to the brain.  Through this process, light is transformed into patterns the brain can interpret.
However, when too much light enters the pupil via glare, it blurs patterns we would otherwise recognize.  The eyes and brain have to strain hard to understand images affected by glare.

3 Types Of Glare:

Discomforting – Mild glare that can be distracting.

Disabling – Brighter than usual lighting (flashlight, spotlight or car headlights).

Blinding – The most severe kind of glare.  Washes out any contrast between the light and its background.
Glare tolerances vary from person to person, with some having a higher sensitivity to glare than others.  Increased sensitivity to light can also be caused by certain medications like diuretics and antibiotics.

When we look at an object, we are seeing the way light interacts and reflects off of it.  The reflective characteristics of a surface material will determine how much light bounces off of it, and the angle of the light source governs the angle at which it reflects.
Two types of reflections are Direct/Specular Reflection and Diffuse Reflection.

As seen in Figure 1, light striking a reflective surface (specular reflection) bounces off at acute angles and retains intensity, while diffuse reflections cause light to spread out.  Glass and mirrors produce specular reflections, while objects with irregular surfaces like brick and wood cause diffuse reflections.

When you notice glare on a computer or TV screen, it typically means that the glare light source is more powerful than the backlight on the device.  Matte screens and pivoting monitors are simple solutions to alleviate glare issues on backlit devices.
Light rays entering your eyes from different angles can contribute to blurred and distorted vision.  The distance between your eye and the reflective surface will also contribute to the amount of glare experienced.

Light Angles

Adjusting the angle of a light source can help to remove glare from a setting.  A little foresight at the planning stage can go a long way to ensuring your occupants aren’t working in a space prone to glare.

There are multiple angles to consider when designing a well-lit workspace, such as:
•Beam angle of the light source
•Illumination angle of the fixture
•Reflection angles from walls and surfaces

High-intensity, narrow-beam lights can lead to glare problems in a space, while a higher number of low-intensity, diffused lights will create a more uniform ambiance.  Indirect lights also provide a quality ambiance by shining onto a surface before diffusing and washing over the intended area.
The materials and textures that surround your lights play an important role in how much illumination your space will retain.  If you have bright lights, think about using matte surfaces to diffuse the light.  If your lights are too dim, you may benefit from a more reflective material.

Light Forms

Natural light is considered by many to be the best kind of light for the workplace, although it is not always possible.  Most offices require the use of artificial light (desk lamps and ceiling lights) to augment natural light and maintain a well-lit environment.
Fluorescent lamps have been popular among employers because they are more efficient than halogens and the “daylight” color causes the human eye to think it is mid-morning – increasing alertness in employees.  LED smart lighting systems take tenant circadian rhythm into consideration by adjusting the light color and intensity of their workspace from dusk to dawn.
Light uniformity is also critical to reducing strain on the eyes in a work environment.  The uniformity ratio accounts for the illumination difference between the brightest and dimmest areas in a space.  The average office uniformity ratio is 3:1, while a parking garage can be closer to 10:1 due to use of high intensity luminaires spread out over greater distances.

The Best Light for a Workplace

Each section of your building should have a unique lighting plan, catered to the amount of light needed.  Lighting designers consider many factors when creating a well-lit space, including:

•Type of task designated for the area
•Reflective nature of wall and surface materials
•General condition of workers’ vision
•Access to natural light

The Illuminating Engineering Society of North America (IESNA) Lighting Handbook of North America considers adequate general lighting to be between 100-200 lux at 30 inches above the floor (approximately desk height).  Areas where workers perform highly detailed visual work, however, should measure between 5,000-10,000 lux.

How to Reduce Glare

If you want to reduce glare in your current workplace:

•Upgrade your lighting - there’s a high likelihood it’s contributing to your discomfort
•Make sure your screen is adjustable or purchase a matte filter
•Hang paintings on highly reflective walls
•Use a desk pad to cover bright spots on a reflective desk

If you’re designing a space, the best way to reduce glare is to:

•Hire a lighting consultant to coordinate with your architects and engineers
•Consider the color and textures of ceilings, walls and desks
•Use indirect or diffused angle lights
•Avoid extreme contrasts in illumination to maintain uniformity

Excellent illumination will account for light angles and glare, while simultaneously making the most of both natural and artificial light.  A room that incorrectly accounts for light angles will lead occupants to experience eyestrain and image distortion.

Focus Earth, a lighting consultant head-quartered in northern California, helps organizations diagnose their existing lighting and recommends adjustments to relieve employee eyestrain and glare.  Beyond the improved work atmosphere, building owners who upgrade their old lamps to LED light systems also enjoy reduced operating expenses and increased property values.

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