Globe Colour Temperature Explained

[alex8337]

WHAT IS COLOUR TEMPERATURE?
Colour temperature is measured in degrees Kelvin (K). The colour temperature of a lamp (bulb) describes how the light appears when the human eye looks directly at the illuminated bulb.

HOW IS COLOR TEMPERATURE MEASURED?
Colour temperature is measured by a unit called the Kelvin (K). The Kelvin thermodynamic temperature scale is defined so that absolute zero is 0 kelvins (K). (Note: The Celsius and Fahrenheit scales are defined so that absolute zero is −273.15 °C or −459.67 °F). Imagine heating a bar of steel and observing the colour of the bar at increasing temperatures. At some point the bar will appear to glow a dull red. As heat is added, the dull red turns to yellow, then to white, then to bluish white, finally to blue.

HOW COLOUR TEMPERATURE WORKS
A light bulb that produces light perceived as yellowish white will have a colour temperature of around 2700K. As the colour temperature increases to 3000K - 3500K, the colour of the light appears less yellow and more white. When the colour temperature is 5000K or higher the light produced appears bluish white. The colour temperature of daylight varies, but is often in the 5000K to 7000K range.

2700-2800K -- WARM LIGHT
When the desired lighting effect is "warm", use light sources in the 2700K - 2800K range. Most common incandescent light bulbs will produce light in this colour temperature range. An exception is the incandescent light bulb with a neodymium coating. The neodymium filters out the yellow and red wavelengths of the visible spectrum leaving predominately blue wavelengths. So even though neodymium light bulbs have a 2800K colour temperature, the light they produce appears to be bluer - similar to daylight and to other light bulbs that product light with colour temperatures in the 5000K or higher range.

3500-4000K -- NEUTRAL BRIGHT LIGHT
When the desired effect is neutral or bright, use light sources in the 3000K - 3500K range.

4000k-5000k -- CLEAR WHITE LIGHT
When the desired lighting effect is "white", use light sources in the 4000K - 5000K range.

5000-6000K -- SIMULATE DAYLIGHT
To give the perception of daylight (bluish white light), use light sources with a colour temperature of 5000K or higher.

6000-6500k -- BLUE
This colour could be illegal in your state or country.

HOW DOES COLOUR RENDERING FIT IN?
It is important to note that colour temperature is not the same as colour rendering. The colour temperature of a light source does not describe or predict the ability of that light source to render colour accurately. For more on this topic, go to the explanation of colour rendering.

[img]http://www.mediacollege.com/lighting/colour/images/colour-temperature.gif[/img]

[chrisco92]

Working for beacon lighting, you guys might know these terms as well by Warm White (2700-3000K), Cool white (3500-4200K) and as stated just Daylight (500-6500K) but all spot on Alex

[Tarquin]

Just to point out - Colour temperature ('K') vs brightness...

It is a common misconception that higher colour temperatures (K’s) produce brighter lights. This is not true. The colour temperature only determines the colour but not the brightness of the light. The Colour Temperature is simply a scale represented by the Kelvin Temperature. Typically, the higher the colour temperature, the closer you get to achieving bluish to purplish light colours.

The higher the Kelvin, the less light output you get (lumens).

With that said, anything over 6000K is basically a waste.
So, what is the best bulb? IMO around 4500K is the best, as it has the highest light output as is the closest you will get to a true white light output - with the highest output for the voltage

[Metalstrix]

[debonaire]

No