Illuminance - Recommended Light Levels
Just thought I'd reproduce this here as useful information. I took it from
engineeringtoolbox.com
Recommended light levels - illuminance - for some common types of working activities
Light Level or Illuminance, is the total luminous flux incident on a surface, per unit area. The work plane is where the most important tasks in the room or space are performed.
Measuring Units Light Level - Illuminance
Illumenance is measured in foot candles
(ftcd, fc, fcd) (or
lux in the metric SI system). A
foot candle is actually
one lumen of
light density per square foot,
one lux is
one lumen per square meter.
- 1 lux = 1 lumen / sq meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
- 1 phot = 1 lumen / sq centimeter = 10000 lumens / sq meter = 10000 lux
- 1 foot candle (ftcd, fcd) = 1 lumen / sq ft = 10.752 lux
Common Light Levels Outdoor
Common light levels outdoor at day and night can be found in the table below:
Condition -
Illumination (ftcd) (lux)
Sunlight
10,000 107,527
Full Daylight
1,000 10,752
Overcast Day
100 1,075
Very Dark Day
10 107
Twilight
1 10.8
Deep Twilight
.1 1.08
Full Moon
.01 .108
Quarter Moon
.001 .0108
Starlight
.0001 .0011
Overcast Night
.00001 .0001
Common and Recommended Light Levels Indoor
The outdoor light level is approximately
10,000 lux on a clear day. In the building, in the area closest to windows, the light level may be reduced to approximately
1,000 lux. In the middle area its may be as low as
25 - 50 lux. Additional lighting equipment is often necessary to compensate the 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.
The table below is a guidance for recommended light level in 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 Theatres
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
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