Lighting

Don’t be impaired by glare. These simple solutions can improve your visual comfort, and reduce glare.

By Craig DiLouie, LC

What you need to know:

• Excessive brightness and brightness contrast can produce glare
• Glare may be direct (from light source) or reflected from an object
• Glare may be irritating or disable vision
• To eliminate glare, move the light source, observer or object/task
• Change the reflectance of the task
• Reduce the brightness of the light source or the brightness contrast by lighting the surround

Brighter isn’t always better. Excessive levels of brightness and contrast can produce glare, which can result in effects ranging from mild irritation to virtual blindness.

Reflected disability glare washes out the pages of this glossy magazine, making it difficult to read.

What Is Glare?

For an object to be visible, light falls on it and is reflected or transmitted to the eye, resulting in both vision and perception. Generally speaking, if you increase the amount of light that falls on the object, you increase its brightness. The object then becomes more visible, particularly if its surround has a low brightness. The result is a high contrast between the object and its surrounding. Too much brightness and contrast can produce glare.

Direct glare is caused by looking directly at a bright light source, such as a lamp (light bulb) or bright window. Reflected glare is caused by light reflecting from a highly reflective surface such as a computer screen, mirror or glossy magazine. Discomfort glare occurs when the observer experiences physical irritation. And disability glare occurs when vision is virtually blocked.

How to Fix It

After the light source is moved, the glare is eliminated and the magazine becomes readable.

The problem of glare can typically be solved by moving or changing the task, moving the observer, or moving or shielding the light source. Consider the glossy magazine page seen in this image. On the left, the image is washed out by reflected disability glare. Simply moving the magazine a little fixes the problem. Alternately, the observer could move a little, or, if the light source is portable, he or she could move the source.

Similarly, suppose your desk in your home office faces a window, exposing you to direct discomfort glare coming in through a window, as well as reflected discomfort glare from sunlight striking a car outside. One solution is to orient the desk so that it’s perpendicular to the window. Another is to shield the light source, in this case by adding manual blinds.

Otherwise, avoid exposed bright lamps and specular (extremely shiny surfaces) that can produce reflected discomfort glare. If shiny surfaces cannot be avoided, consider a very diffuse light source such as indirect light. If there is an exposed lamp, shield it or use a light that is not as bright. Or simply move the light source above the field of view, where direct glare is less likely to be noticeable.

A final tip is to reduce extreme contrast either by reducing the brightness of the light source or increasing the brightness of its surround. For example, if a window appears very bright, consider putting some light on the wall around it, which will reduce contrast and thus reduce the potential for glare.

* Photos from IES DG-29