LED color temperature knowledge popularization

　　The more blue the light is, the higher the color temperature is; the more red the light is, the lower the color temperature is. The color of the light changes with time during the day: 40 minutes after sunrise, the light is yellower and the color temperature is 3,000K; the sunlight at noon is white, rising to 4,800-5,800K; at noon on a cloudy day, it is about 6,500K; before sunset, the light is reddish and the color temperature drops to 2,200K. The correlated color temperature of other light sources is not an accurate color comparison because the correlated color temperature is actually the evaluation value of the light color performance of the light source when the black body radiation approaches the light color of the light source. Therefore, two light sources with the same color temperature value may still have some differences in the appearance of light color. The color temperature alone cannot understand the color rendering ability of the light source for an object, or how the color of the object is reproduced under the light source.

　　Correlated color temperature of different light source environments

　　Northern clear sky 8000-8500k

　　Cloudy day 6500-7500k

　　Summer noon sun 5500k

　　Metal halide lamp 4000-4600k

　　Afternoon sunlight 4000k

　　Cool color camping light 4000-5000k

　　High pressure mercury lamp 3450-3750k

　　Warm color camping light 2500-3000k

　　Halogen lamp 3000k

　　Tungsten lamp 2700k

　　High pressure sodium lamp 1950-2250k

　　Candle light 2000k

　　Different light sources have different color temperatures, and the light colors are also different. Color temperatures below 3300K create a steady atmosphere and a warm feeling; color temperatures between 3000--5000K are intermediate color temperatures, creating a refreshing feeling; color temperatures above 5000K create a cold feeling. Different light colors from different light sources create the best environment.

　　Color temperature is the feeling of the human eye to a light source or a white reflective object. It is a feeling of complex factors of physics, physiology and psychology, and it varies from person to person. Color temperature can be changed artificially on television (light source) or photography (reflective object). For example, in photography, we use a 3200K incandescent lamp (3200K), but we add a red filter to the lens to filter out a little red light to make the photo look a little lower in color temperature. For the same reason, we can also reduce a little red on TV (but reducing too much will also affect the performance of normal red) to make the picture look a little higher in color temperature.

　　The preference for color temperature depends on the individual. It is related to the scenery we see every day. For example, people near the equator see an average color temperature of 11000K (8000K (dusk) ~ 17000K (noon)), so they prefer high color temperature (which looks more realistic). On the contrary, people in higher latitudes (with an average color temperature of about 6000K) prefer low color temperature (5600K or 6500K). That is to say, if you use a high color temperature TV to show the scenery of the Arctic, it will look bluish; on the contrary, if you use a low color temperature TV to watch the subtropical scenery, you will feel that it is a bit reddish.

　　How is the color temperature of a TV or display screen defined? Because the average color temperature of the scenery in China is about 8000K to 9500K throughout the year, the TV stations shoot programs based on the audience's color temperature of 9300K. However, because the color temperature in Europe and the United States is different from ours, the average color temperature of the year is about 6000K as a reference for production. So when we watch those foreign films, we will find that 5600K to 6500K is the most suitable for viewing. Of course, this difference makes us feel that the color temperature of European and American computer or TV screens is reddish and warm, which is a bit uncomfortable.

　　That is, the color temperature. People with dark eyes see 9300K as white, but people with blue eyes see it as bluish. People with blue eyes see 6500K as white, but we Chinese see it as yellowish.