What a color temperature?Date:2017-08-09
What a LED light bulbs color temperature?
Color temperature is an important aspect of color appearance that characterizes how “cool” (bluish) or how “warm” (yellowish) nominally white light appears. Correlated Color Temperature (CCT) is a metric that relates the appearance of a light source to the appearance of a theoretical black body heated to high temperatures. As a black body gets hotter, it turns red, orange, yellow, white, and finally blue. The CCT of a light source, given in Kelvin (K), is the temperature at which the heated black body most closely matches the color of the light source in question. It characterizes the color of the emitted light, not the color of illuminated objects. Like many color appearance metrics, CCT distills a complex spectral power distribution to a single number. This can create discord between numerical measurements and human perception. For example, two sources with the same CCT can look different, one
appearing greenish and the other appearing pinkish (see Figure 2). To address this issue, the American National Standards Institute (ANSI) references Duv, a metric that quantifies the distance between the chromaticity of a given light source and a blackbody radiator of equal CCT.3 ANSI has established Duv tolerances for LED lighting products producing white light.
Today’s LED systems can produce white light throughout the range of CCTs typically used in general lighting, including both interior and exterior applications. Due to differences in quantum efficiencies, higher-CCT LED sources tend to be more effi cacious than lower-CCT alternatives within the same product family.Some mixed or hybrid LED products feature independent control of the different components to allow for dynamic adjustment of CCT.
HOW TO READ THE CHART
The curved line is called the “Black Body Curve” and
represents the color temperature of an object (for instance a piece of steel) that is heated until it gives off light. The curve begins at the extreme right of the of the chart and moves to the left. As the steel is heated, its color (Color Temperature) changes from black to dull red, orange, yellow, white and finally blue, as the heat increases.
The lines intersecting the black body curve represent the range of points on the chart that will result in a specific color temperature.
A Metal Halide lamp with Chromaticity coordinates of
X=0.396, Y=0.402 shows that the lamp has a 3800K Color Temperature (shown by the red “X”).
*Kelvin is a temperature scale in which zero occurs at absolute zero and each degree equals one Kelvin.
How important is color temperature?
Color Temperature is indicated in units called Kelvin and its value determines whether light bulbs produce warm or cold light. This guide shows how LED and energy-saving light bulbs can have different color temperatures.