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LED Color Temperature

Sep 20, 2019

LED Color Temperature

    Since most of the light emitted by the light source is collectively referred to as white light, the color table temperature or the correlated color temperature of the light source is used to refer to the degree to which the light color is relatively white to quantify the light color performance of the light source. According to Max Planck's theory, a standard black body with complete absorption and radioactivity is heated, and the temperature gradually increases, and the luminosity changes accordingly; the Black body locus on the CIE color scale shows the process of black body red-orange-yellow-yellow-white-white-blue-white. The temperature at which the black body is warmed to the same or close to the light source is defined as the correlated color temperature of the light source, which is called the absolute temperature K (Kelvin or Kelvin) (K=°C+273.15). Therefore, when the black body is heated to a red color, the temperature is about 527 ° C, that is, 800 K, and other temperatures affect the color change.

    The more the light color is blue, the higher the color temperature; the reddish color is the lower the color temperature. The color of the light in the day also changes with time: 40 minutes after sunrise, the light color is yellower, the color temperature is 3,000K; the midday sun is white, rising to 4,800-5,800K; At noon on cloudy days, it is about 6,500K; before sunset, the color is reddish and the color temperature drops to 2,200K. The correlated color temperature of other light sources, because the correlated color temperature is actually the black body radiation approaching the light source color, the evaluation value of the light source color performance is not an accurate color contrast, so the two light sources with the same color temperature value, There may still be some differences in the appearance of the light color. The color temperature alone cannot understand the color rendering ability of the light source to the object, or how the color of the object is reproduced under the light source.

Correlated color temperature for different light source environments

Cloudy day 6500-7500k

Summer sunlight at noon 5500K

Metal halide lamp 4000-4600K

Sunlight in the afternoon 4000K

Cool color camp light 4000-5000K

High pressure mercury lamp 3450-3750K

Warm color camp light 2500-3000K

Halogen lamp 3000K

Candle light 2000K

The color temperature of the light source is different and the light color is different. The color temperature is below 3300K, there is a stable atmosphere, the feeling of warmth; the color temperature is 3000--5000K for the intermediate color temperature, and there is a refreshing feeling; the color temperature has a cold feeling above 5000K. Different light colors of different light sources constitute the best environment.

Color temperature is the human eye's perception of illuminants or white reflectors. This is a feeling of physics. The complex and complex factors of physiology and psychology are also different from person to person. The color temperature can be changed in a human way on a TV (illuminator) or photography (reflector). For example, we use a 3200K incandescent heat lamp (3200K) for photography, but we add a red filter to the lens. Filtering through a little red light makes the photo look lower in color temperature; the same reason, we can also reduce a little red on the TV (but reducing too much will also affect the normal red performance) to make the picture look a little warmer.

    The preference for color temperature is determined by people. This is related to the daily scenery we see. For example, in the people close to the equator, the average color temperature seen every day is 11000K (8000K (dusk) ~ 17000K (noon)). So I prefer high color temperature (which seems more realistic). Conversely, people with higher latitudes (average color temperature of about 6000K) prefer low color temperature (5600K or 6500K), which means if you use a high The color temperature TV to show the scenery of the Arctic, it seems to be partial green; on the contrary, if you use a low color temperature TV to see the subtropical style, you will feel a little reddish.

    How is the color temperature of a TV or display screen defined? Because the average color temperature in China's scenery is about 8000K to 9500K throughout the year, the TV station's production of the program is based on the viewer's color temperature of 9300K. However, because the color temperature in Europe and America is different from ours, the average color temperature of the whole year is about 6000K. Therefore, when we look at those foreign films, we will find that 5600K~6500K is the most suitable for viewing. Of course, this difference makes us feel that when we see the screen of a computer or TV in Europe and America, we feel that the color temperature is reddish and warm, and some are not suitable.