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LED Education
General Led Info
* The True Cost of LED Lighting
* Save money on your utility bill
* The Death of the Light Bulb
* Why is my electricity bill so high?
* Busting Electricity Myths
* Color Rendering Index (CRI)
* Tackling Light Pollution with Outdoor Lights
* Pupil Lumens and their impact on the choice of lighting
* Understanding Color Temperature
* LED versus Traditional Lamps: A fight between unequals
* What is an LED?
* The 2007 USA Energy Bill
* What is the different between ETL and UL Listing?
* US Made Commercial LED lights
* What influences the lifespan of an LED Light?
* What is the IP rating system?
* Lighting Language - Basics
* Lighting Maintenance Factor
* (LED) Technical Terms
* The High Cost of Doing Nothing - Why Wouldn't you Convert to LED?
* The Truth About LED Lumens
Going Green
* Reduce your energy bill using Energy Saving Lights
* How to Reduce your Carbon Footprint
* What you need to know about Alternative Energy Sources
* Save Money with Energy Efficient Lighting
* Why should schools be interested in reducing their energy consumption?
* LED's Role In Slashing Your Electricity Bill
* Light Management Systems - Upgrading the efficiency of Lighting Systems
Induction Lights
* What is induction lighting?
LED Street Lights
* What you need to consider with Street Lights
* The Cost of Street Lights
* Part I - The Complete Guide to LED Street Lights
* Part II - The Complete Guide to LED Street Lights
LED Tube Lights
* The Complete Guide to LED Tube Lights
* LED Tube Lights I - Why LED tubes are a good replacement for fluorescents
* LED Tube Lights II – Mercury from Recycled Fluorescent Tubes
Grow Lights
* Facts about Grow Lights
* Why we need to consider indoor gardening
LED Par Lights
* Understanding PAR Lights
LED Sport Lights
* High Quality LED High Mast Lights And Sport Lights
LED Lights for Business
* Lighting for your Farm and Ranch
* Lighting Strategies for Retail Stores
* Lighting for Commercial Companies Sound Financial Sense and CSR
* The best lighting choice for hospitals
* Energy Efficient lights for Warehouse Applications
* How to Reduce Office Energy Costs
CFL's and Flourescent Lights
* LED vs CFL: An Exhaustive Comparison
* Settling the Mercury Emission Debate

Understanding Color Temperature

Lamps are often rated by:

  • Power consumption and light output – in Watts (Unit of electricity consumption), Lumens, Lux or Candela (Units of light output), Lumens per Watt (A derived unit that indicates the luminous efficiency of the lamp).
  • Color Rendering Index – A measure of how efficient is a lamp at reproducing colors.
  • Color Temperature – an indicator of visual light color

Before we start, discover the difference between Color Rending Index and Color Temperature by clicking here. Then come back and continue!

Of late, a new parameter called ‘Pupil Lumens’ has entered the picture. The light output of a lamp is expressed in photopic lumens. Pupil lumens on the other hand measure the impact of different wavelengths of the eye on vision under Mesopic light conditions.

You can refer to other resources on this site to know more about power consumption, light output, Color Rendering Index and Pupil Lumens.  Below is a discussion of Color Temperature meant to help you choose the right LED technology product.

Color Temperature

Color temperature of a light source is “the temperature of a black body radiator in Kelvin (K) that radiates light of a hue that is similar to that produced by the light source.” This definition may be a bit confusing for people not familiar with the physics behind light. A simpler explanation of color temperature would therefore be more appropriate.

When the first developments in lighting technology occurred, the only way to produce light was to heat an object. When an object was heated – either by passing a current through an electric wire or by other means – it first became ‘red hot’ and then went on to become ‘white hot’ as the heating continued. 

A ‘red hot’ object has a temperature close to 600 degrees centigrade. By comparison, a ‘white hot’ object may have a temperature of 7000 degrees or more. If you have seen a glowing ember (600 centigrade temperature, with very little light output), it is easy to understand that at lower temperatures almost all the energy is converted to heat. At higher object temperature, the production of light improves. Thus, energy from the sun consists of 40% light and 60 % heat while a light bulb emits 10% or less energy as light and 90% as heat.

Here are the temperatures of a few light sources

 Light Source
 Glowing ember  900K
 Match flame 1700K
 Incandescent Bulb 2700-3300K
Sun at sun rise or sun set  3000K
Sun at noon  6500K


The incandescent bulb is very close to the ideal black body radiator. Other sources of light including metal halide, fluorescent and LED lights produce lights by processes other than heating. Instead of color temperature, the term Correlated Color Temperature (CCT) is at times applied to these light sources and is a good yardstick for comparing different sources of light.

Lights of 3 different Color Temperatures. Note that the light from 6000K lamp is bluish in color.

Importance of Color Temperature

Color temperature is particularly important in photography and desktop publishing. Differences in color temperature can result in variations in color rendering.

In homes and offices, color temperature of lights is important as different colors of light have different psychological impacts and are designated as ‘warm’ or ‘cool’. Ironically, the so-called ‘warm lights’ have a lower ‘Color Temperature’ while the ‘cool lights’ have a higher ‘Color Temperature’. Warm and cool thus refers not to the color temperature but to psychological attributes of lighting. The light from wood burning fires and incandescent bulbs is yellowish in color.

The human mind, conditioned by thousands of years of social evolution, accepts yellow-ish light as warm and inviting. On the other hand, day white light is associated with cleanliness and efficiency - as in hospitals. IT is also depending on cultural and regional backgrounds as people form countries nearer to the equator prefer cold white light sources than warm white lights.

The choice of light color temperature is governed by the look you wish to create in an area. Lights of different color temperature are described by their similarity to known sources or with typical adjectives. The table below can help you choose the right lamp for your needs

Lamp Color Name Apparent Color Temperature (Kelvin) Characteristics and Examples Common Adjectives Used to Describe the Light Best Location
Warm White  2700-3200K Similar to incandescent bulb, yellowish light best  for accentuating skin tones and color of wooden objects Friendly, warm, inviting, intimate, relaxing Best for areas that need low light intensity like Bedrooms, lounges, restaurants, office lobbies, boutiques, reception area etc.
Natural White  4000-4500K Similar to early morning sunlight, Xenon lamp for automotive use Neat and clean, Natural tone Best choice for high light intensity applications like  Surgical lights, indoor photography, Laundry, Office etc.
 Day White  5500-6000K Typical day light, Flash light. Crisp light, efficient, brightly lit, natural outdoor Retail stores, Factories, Printing, artist studio, Schools, Offices, indoor grow lights, photography
 Cool White  7000-7500K Best contrast but least flattering to the skin, may need mixing with light from a warm white lamp. Bright light, bluish light Special applications needing high light intensity and good color rendition like art Galleries, museums, showcases for precious stones and jewelry


Want to see how much LED can save you? Click here to try our new and simple to use Energy Savings Calculator

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