Imagine a sunset sky, the beautifull setting sun which makes the the whole sky glow in a soft orange tone. In our experience, it is a very nice, comforting color. This lightcoulour is expressed as the color temperature of light. It differs from warm to cool, from redish to more blue light, in degrees Kelvin. There is another factor of importance for good lighting, besides color temperature. That is the way colors are reflected as natural as possible. What are critical factors in LED lighting;
Color of light is measured in degrees Kelvin (K). A lower number, gives a warmer color. Cool white has 6500K, we experience this color as blue light. Neutral white has a number of 4000K. And if we switch to a warmer color; an un-dimmed light source has 2700K and a filament light bulb about 2300K. We perceive this as comfortable (orange-like) light. These color indexes of light-sources are determined with a spectrum analyzer.
Next to color temperature, there is another important criterium in LED lighting, which influences the way we percieve light. It is color rendering index, expressed in CRI of RA-value. This number indicates the effect of a light source on the color reflection of an object. Compared to the color reflection of the same object in daylight. So to speak, is the color reflected in artificial light the real color? This color rendering index varies from 1 to 100. A CRI of 100 is almost equal to natural (sun) light and gives the objects best color reflection. Good quality LED lightsources have an index of 80 as a minimum to 90 - 95.
By comparing a number of reference colors in the light source with another light source (for example the sun or a light bulb) the RA-factor is determined.The difference is the deviation down from a 100. A lower numbers means the color differs more from the natural color. For example, blue will not look bright but grey toned.
The color number is a combination of these two values. The first number indicates the color rendering index, the other numbers the color temperature. Example: color 840. This light source has a color rendering index of 80 (or more) and a color temperature of 4000K.
Which color temperature to chose depends on type of space and function. Generally we like an orange-red toned light for a nice athmpshere in our living room or restaurant. In offices, a neutral white color makes a better working space, and for a treatment rooms an even cooler color temperature is often applied. A good color rendering index is always important. As you like your food to look as good as home as in the shop. And your shirt or dress to be outside just as colorfull as in the dressing room. If there are specific questions about the application of light, be sure to get a specialist advice. To get the best result.