The lux (lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square metre.
In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. Illuminance levels can be measured with a lux meter or predicted through the use of computer simulations (e.g. DiaLUX).
To place the amount of 1 lux into context, examples of the wide ranging lux in natural ambient light conditions are given in the table below:
Sunlight provides between many thousands of lux to only a few hundred depending on the weather conditions & time of day.
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 it may be as low as 25 - 50 lux. Additional lighting equipment is often necessary to compensate the low light levels.
Depending on activity required light level is commonly in the range 500 - 1000 lux. For precision and detailed works, the light level may need to be in the range of 1500 - 2000 lux.
The table below is a guide for recommended light level in different areas:
General Areas
Circulation Areas
Offices
Kitchen
Retail
Engineering
Services
Packing, Storage & Dispatch
Generally, factors that affect the effectiveness of illumination are quantity and quality of light, amount of glare, contrast and shadows. Each factor must be adjusted according to the scenario to optimize illumination for wellbeing, productivity, emergency, safety, operations, and security situations, etc.
Lighting Standards also serve to address concerns associated with the design, placement, installation, and minimum energy requirements and efficient allocation of illumination in different locations with different purposes, as well as the efficiency, durability, cost, and maintainability.
It is advised you always asking for a light calculation to confirm the light levels. Light calculation is a very useful tool to determine the best layout and predict the light levels in a given space. If you require help getting light calculations down please contact us on 020 3239 0798
