The ability to "see" at work depends not only on lighting but also on:

• The time to focus on an object.  Fast moving objects are harder to see.
• The size of an object.  Very small objects are harder to see.
• Brightness.  Too much or too little reflected light makes objects harder to see.
• Contrast between an object and its immediate background.  Too little contrast makes it harder to distinguish an object from its background.

Common Lighting Problems

 Poor lighting can cause several problems such as:

• Insufficient Light - not enough light for the need
• Glare - too much light for the need
• Improper Contrast
• Poorly Distributed Light, and
• Flicker

Insufficient Light

Poor lighting can be a safety hazard - misjudgement of one's position, shape or speed of an object can lead to accidents and injury. 

Poor lighting can affect the quality of work, specifically in situations where precision is required, and overall productivity.

Poor lighting can be a health hazard - too much or too little light strains eyes and may cause eye discomfort (i.e. burning, etc) and headaches.

Glare

Glare is a common lighting problem.  Glare is what happens when a bright light source or reflection interferes with how you are "seeing" an object.  In most cases, your eyes will adapt to the brightest level of light.  When this adaptation happens, it becomes harder to see the details in the duller or darker areas of the work space (even though they are sufficiently lit).  Glare can cause annoyance and discomfort, and can actually decrease a person's ability to see.

Reflected glare ('A & B' in picture below) is caused by:  

• Light reflected from polished, shiny or glossy surfaces
• The glass on picture frames, or windows at night and
• Computer screeens

Direct glare ('C' in picture below) is caused by: 

• Very bright light from poorly positioned light fixtures or
• Sunlight

Improper Contrast

There are two types of contrast problems - the first occurs when there are very different light levels from one area to another, and the other is contrast between the color of objects.

The immediate work area should be brighter than surrounding areas.  If the surrounding area is brighter than the work area, your attention will be distracted away from the work area.

The contrast between color of objects, such as between the print itself and the paper or text and background on computer screens, can also cause problems.  Too little contrast between print and paper - or characters on a computer screen and the background - makes reading tasks difficult and can contribute to eyestrain and headaches.  In an industrial setting an example would be that moving and stationary machine parts are hard to distinguish if they are the same color.

Poorly Distributed Light

When light is poorly distributed, parts of the ceiling and general surroundings will seem dark and gloomy.  Substantial differences in light levels force your eyes to readjust when moving from one light level to the other.  Workers may find it difficult or impossible to see properly.

You can detect poorly distributed light by: 

• Looking for dark areas and uneven light
• Using a light meter to check the illumination at various points throughout the workplace 

Flicker

Light flicker refers to quick, repeated changes in light intensity - light that appears to flutter and be unsteady.  It is caused when the voltage supplied to a light source changes or when the power line voltage itself fluctuates.  The severity of the flicker depends on several factors such as:

• How often and regularly the voltage fluctuates
• How much of a voltage change occurs
• The kind of light (incandescent, fluorescent, etc)
• The gain factor of the lamp (the measure of how much the light intensity will change when the voltage fluctuates)
• The amount of light in the lighted area (ambient light levels).