No matter we are lighting up the commercial parking lot, industrial areas like factory, or even stadiums, we need to have proper lighting uniformity to improve user’s perception.
Maintaining an ample brightness (lux level) is important, however, many users would omit the measurement and calculation of light uniformity ratio. If the uniformity is very low for the outdoor or indoor lighting, the citizens, workers, or athletes might feel uncomfortable, and thus their vision is affected.
What is Lighting Uniformity
1. Definition & U1 U2 Light Uniformity Equation
We can measure the brightness lux level by using the lux meter, and then we can get the figure so a certain of area. But how about uniformity data? Yes, you are right. It is very unlikely to measure this parameter by a single device. It is because lighting uniformity is defined as the ratio between minimum to average lux, or minimum to maximum lux. Lux is the unit of illuminance, indicating the actual brightness received on the ground.
In general, the lighting uniformity equations governing U1, U2 & illuminance (lux) are
U1 = EMin ÷ EAverage
U2 = EMin ÷ EMaximum
U & E stands for uniformity & illuminance respectively.
Thus, we can observe from the above formula that the two types of light uniformity are basically the ratio between the illuminance, or simply the lux level. It is quite useful to use this uniformity ratio to describe how the lights are evenly distributed on the ground. If the difference between minimum and average lux is small, then the ratio is high, which gives better light uniformity.
2. Poor Vs Good Light Uniformity
Let’s have a quick look on the meaning of good lighting uniformity. For the photos on the left-hand side, we can see there are bright spots and dim areas in the warehouse. So, the workers might not be able to see clearly in such the dark regions, and they might easily get injured. On the contrary, the area having good light uniformity means the whole floor is illuminated evenly. Since the ceiling flood lights are illuminating the floor in different directions, we can also achieve the shadowless illumination.
The recent research revealed that the high lighting uniformity improves not only the productivity & safety of workers, but the vision experience of spectators in sports stadium event.
Contact us to get the free lighting design having high uniformity.
3. How to Calculate Lighting Uniformity
Let’s do a quick math on calculating the LED lighting uniformity in real situation. By considering the football field DIALux illuminance chart,
we have the following data. The figures in the chart represents the lux levels in different sampling points.
Thus, by using the formula, we can calculate U1 = Minimum / Average lux = 551 / 624 = 0.88, and U2 = Minimum / Maximum lux = 551 / 708 = 0.78.
The maximum lighting uniformity is 1, which means the lux levels in all the sampling points are the same. However, it is very unlikely to achieve this maximum value for artificial lighting.
4. Different Lighting Uniformity Standards
What are the lighting uniformity requirement in different areas? It depends on the natural & type of field. Taking football field as the example, it has the following standard.
|Nature of Sports Field||Illuminance||U2 Light Uniformity Required|
|Class III (National Competition)||700 to 1000 lux||≥ 0.7|
|Class II (Leagues)||400 to 700 lux||≥ 0.6|
|Class I (Training Ball Field)||200 to 400 lux||≥ 0.5|
It is observed that the lighting uniformity standard increases with the competition level of the sports field. If the football field is designed for training or recreational purpose, then the uniformity & illuminance requirement would be lower. On the contrary, if the field is holding the national, or televised matches, the lighting requirement would be more rigorous.
Commercial & Industrial Lighting Uniformity Requirements
|Area||Light Uniformity Standard|
|Airport||0.2 to 0.3|
|Running Track||0.3 to 0.5|
|Warehouse Lighting||0.4 to 0.6|
|Parking Lot||0.4 to 0.5|
|Office||0.4 to 0.6|
|Seaport||0.3 to 0.4|
|Highway||0.4 to 0.6|
In fact, it does no harm to have high uniformity lighting because it improves the vision of worker or road users at night. However, the cost of luminaires would be higher because we will need a more complex lighting system to get the highly uniform illumination.