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Understanding LED Lighting

The importance of accurately measuring the light emitted from a LED light bulb has been highlighted by the frequent overstating of light levels (intensity or outputs in lumens) by various suppliers as well as the variability in the colour of the LED light known as colour temperature. Understanding the measurement units of LED light is the first step in understanding the product and whether or not that product is suitable for you.

Aside from knowing that the LED light bulb or luminaire is going to do what the specifications state, the other important area is knowing what sort of LED light you need to create adequate ergonomics including good visibility or a comfortable environment whilst maintaining a high level of efficiency. After all you are changing to LED lights either because of the energy saving advantage or the long life of the product. Nevertheless you want the LED lamp to do what your old lamp did for a fraction of the running cost and if possible you want it to do an even better job at LED lighting your home, office, factory or shop.  

In this section we will examin the following LED light measurement and concepts:

  1. LED Light Colour Rendering Index (CRI) - how do your products or furnishings look under the led light?
  2. LED Light Colour temperature - what is the colour of the LED light?

  3. LED Light Power and Energy Efficiency in Lumens/Watt

  4. LED Light Brightness or Lumen levels 1 - Total Downwards Luminous Flux, overall intensity

  5. LED Light Levels Brightness 2 - Be Careful of Manufacturer Specifications

  6. LED Light Brightness - Lux and Lumen levels

  7. LED Light Optics, beam angle and angular intensity affecting beam spread
For a more general overview you should read the LED Buying Guide Checklist and associated important sections including "Passive Cooling Methods" and "Critical Design Elements" in the LED Buying Guide.

References and Further Reading:

How is LED lighting different from other energy-efficient lighting technologies? In Solid State Lighting, LED Basics. US Department of Energy. www1.eere.energy.gov

Energy Efficiency of LEDs. Building Technologies Program. Solid-State Lighting Technology Fact Sheet. US Department of Energy. www.eere.energy.gov

LED Frequently Asked Questions. May 2011. US Department of Energy. www.eere.energy.gov

New Reasons to Change Light Bulbs. March 2013. The New York Times

next.gif LED Light Colour Rendering Index (CRI) - how do your products or furnishings look under the led light?