Understanding Light Level

Why are workplace light levels Important?

The Workplace (Health, Safety and Welfare) Regulations state that every workplace shall have suitable and sufficient lighting and that, so far as is reasonably practical, this lighting shall be by natural light.

The task light level depends on natural ambiance light, total lamp lumen, height of lamp installation and type of reflector used. A simple way to gauge the lux level is to use the lux metering apps on a tablet or mobile phone. Some uses the camera to check for light flickers as well.

Picture 1: A picture of T8 LED tube with high uniformity and flicker free.

The following picture is an example of a bad and good lighting installation of the same corridor. The positioning of the light troffers are the same. Notice the picture on the left has very pronounced shadow effects on the walls, near the ceiling and dark spots on the walkway. The picture on the right depicts a different light ambiance with the same height installation.

Picture 2: Two different light types on the same position, height along the same corridor. Notice the shadow effects.

So how does reading in the dark affect your eyes?

According to most eye doctors, it won’t cause lasting damage. Reading in low light won’t cause a decline in vision, it can lead to eye strain.

Just like any muscle in the body, the eyes can get weak when overworked. Challenging visual work, like reading in dim light, causes the eyes to become tired faster than they normally would. Some symptoms of eye strain include tired eyes, headaches, itchy eyes, blurred vision, and increased sensitivity to light.

Light Level or Illuminance is the total luminous flux incident on a surface per unit area. The area – the work plane – is where the most important tasks in the room or space are performed.

 

Common outdoor light levels at day and night:

Condition Illumination
(ftcd) (lux)
Sunlight 10000 107527
Full Daylight 1000 10752
Overcast Day 100 1075
Very Dark Day 10 107
Twilight 1 10.8
Deep Twilight 0.1 1.08
Full Moon 0.01 0.108
Quarter Moon 0.001 0.0108
Starlight 0.0001 0.0011
Overcast Night 0.00001 0.0001

Indoor Light Levels

The outdoor light level is approximately 10000 lux on a clear day. In a building in the area closest to the windows the light level may be reduced to approximately 1000 lux. In the middle area it may be as low as 25 – 50 lux. Additional lighting is often necessary to compensate low levels.

Earlier it was common with light levels in the range 100 – 300 lux for normal activities. Today the light level is more common in the range 500 – 1000 lux – depending on activity. For precision and detailed works the light level may even approach 1500 – 2000 lux.

Recommended light levels for different work spaces:

Activity Illumination
(lux, lumen/m2)
Public areas with dark surroundings 20 – 50
Simple orientation for short visits 50 – 100
Working areas where visual tasks are only occasionally performed 100 – 150
Warehouses, Homes, Theaters, Archives 150
Easy Office Work, Classes 250
Normal Office Work, PC Work, Study Library, Groceries, Show Rooms, Laboratories 500
Supermarkets, Mechanical Workshops, Office Landscapes 750
Normal Drawing Work, Detailed Mechanical Workshops, Operation Theaters 1,000
Detailed Drawing Work, Very Detailed Mechanical Works 1500 – 2000
Performance of visual tasks of low contrast  and very small size for prolonged periods of time 2000 – 5000
Performance of very prolonged and exacting visual tasks 5000 – 10000
Performance of very special visual tasks of extremely low contrast and small size 10000 – 20000

Summary

As consumer, we purchase lamps based labels. In some cases, the seller pushes the one that gives them highest commission.

What is the right approach to select the correct type of lamp?