How LED lamp is made and measured

The inspiration of this blog is to create awareness that lighting replacement has to be done with care. It is not about looking for the cheapest solution but selecting the correct lamp to create the same lighting condition as defined by lighting architects to maintain a conducive working environment.

My previous blog discussed about light level is dependent on the task requirements; however, over time, due to light decay or faulty lamp replacements; the light condition changes. For the less technical, it is about becoming aware of the deteriorated light level condition and providing ‘look and feel’ feedback.

I had an opportunity to participate in a corporate social responsibility (CSR) program to help financial and replace fluorescent tubes for not-so-well funded schools. During the technical due diligence and periodic assessment including talking to the younger students, we could see the positive transformation due to brighter lights.

Light decays over time

Fig. 1: Light Decay Over time

The key learning:

Why was there almost no feedback on the previous poor lighting conditions? Who is responsible to help the school children?  Do we expect the young child to feedback about the lighting conditions? What are the teachers and parents’ role to help connect the dots?

For the more technical, the following are some references to show case How LED Tube is Made and How LED lamp is characterized or measured and yet we see vast disparities. US DOE publishes T8 bench marking report showing disparity.


    1. How LED Tube is Made Video?

    1. How LED Lumen is measured?


Different Types of LED tubes

Fig. 2: Different types of LED tubes.

Fluorescent replacement tubes comes in various sizes (T5, T8, T12) and lengths ( 2 ft, 4 ft, 5 ft). T5 is 5/8, T8 is 8/8 and T12 is 12/8 of an inch. The form factor of LED tubes may be the same; the design approach could vary significantly. Fig. 1 shows a collage of 4 foot tubes.


As consumers, we purchase our lamp based on label. The product specifications has lamp light output in lumens, lamp power in Watts, lamp efficacy or efficiency in lumens per watt (lm/W), color accuracy with reference to sunlight at 100, and the color temperature in Kelvin (K).

LED Lamp characteristic label

Fig. 3: LED Lamp label showing various characteristics of the LED Lamp

A traditional fluorescent tube requires a ballast to operate. The fluorescent tube may be specified at 32W; however, the total power to operate the system will determine the electricity bill. In general, a typical fluorescent with magnetic ballast consumes about 44 W power. In contrast, T8 LED is an integrate system and it does not requires a ballast to operate.

Key takeaways

  • Not all T8 LED lamps are the same
  • Lux and light accuracy at task level is the most important criteria to ensure spec conformance
  • Given a fixed lumens, the higher the lm/W, the more efficient the lamp
  • The efficiency affects the monthly electricity bills; thus, Operating cost is more important than initial cost of the lamp.

In short, it is our responsibility regardless of what is in the market.