Monday, February 10, 2014

Three Things To Know When Choosing Led Light Bulb

Led light bulbs are getting more and more popular and they are slowly replacing standard incandescent light bulbs.

Because their low power consumption they are perfect for use with home PV solar panels and
small wind turbines.

While everyone is switching to led light bulbs because of low power consumption and luminous efficacy, people are forgetting about color temperature, luminous flux and color rendering index.



This attributes for light bulb are important when choosing light bulbs for office or work space environment.

Color temperature


The color temperature of a light source is the temperature of an ideal black body radiator that radiates light of comparable hue to that of the light source. In practice, color temperature is only meaningful for light sources that do in fact correspond somewhat closely to the radiation of some black body, i.e. those on a line from reddish/orange via yellow and more or less white to blueish white; it does not make sense to speak of the color temperature of e.g. a green or a purple light. Color temperature is conventionally stated in the unit of absolute temperature, the kelvin, having the unit symbol K.

Table 1 show values of color temperature that are used in different environments.

Table 1. Values of color temperature that are used in different environments


Table 2 show alternative name for color temperature (this names may be uses on light bulb packaging instead of values in kelvins).

Table 2. Alternative name for color temperature


Figure 1 shows difference between different color temperature.

Difference between different color temperature [1]

Luminous flux

In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of electromagnetic radiation (including infrared, ultraviolet, and visible light), in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.

Table 3 show values of luminous flux used in used in different environments by EN 12464-1:2002 standard [2].


Table 3. Values of luminous flux used in used in different environments

Color rendering index

Color rendition index, is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications such as photography and cinematography.

Table 4 show values of color rendering index used in used in different environments by EN 12464-1:2002 standard [2].


Table 4. Values of color rendering index used in used in different environments


References:
[1] - Picking Color Temperature For Your Light Bulbs.
http://www.greenoptions.com/a/picking-color-temperature-for-your-light-bulbs
[2] - EN 12464-1:2002, Light and lighting – Lighting of work places Part 1: Indoor work places


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