The difference between color temperature and correlated color temperature

Color temperature refers to the color change experienced by human eyes under different energies of light waves.

In the calculation of color temperature, Kelvin is used as the unit, and 0° Kelvin of blackbody radiation = -273° Celsius is used as the starting point for calculation.

Heating the black body, as the energy increases, it will enter the realm of visible light. For example, at 2800 ° K, the color light emitted is the same as that of a light bulb, so we say that the color temperature of the light bulb is 2800 ° K.

The color temperature changes in the visible light field, from low color temperature to high color temperature, are orange-red --> white --> blue.

Color temperature is a numerical value that measures and identifies wavelength. Different wavelengths of light present different colors of light, so the color temperature of the light source has a great impact on color photography, especially natural light. The color temperature will change with changes in time, season, and geographical location. When it is necessary to correctly restore the color of the subject, such as reproducing photos or calligraphy and painting works, taking ID photos, etc. When shooting, you must pay attention to ensure that the color temperature of the light is consistent with the color temperature required by color film.

Color temperature does not refer to the hot or cold degree of light. The application of color temperature in photography is to measure the color components contained in light. The classic definition of color temperature refers to: when the color of the light emitted by the light source is consistent with that of a black body (an object that neither reflects nor transmits under the action of radiation, but absorbs all the radiation falling on it. When the black body continues to be heated, the temperature As it continues to rise, the emitted light has a certain color, and its changing sequence is red-yellow-white-blue). When the color of the radiated light is the same at a certain temperature, the temperature of the black body is called the color temperature of the light source. Referred to as color temperature.

When sunlight shines 40° above the horizontal line in a cloudless atmosphere, the color temperature is 5500K. In 1983, the World Organization announced this as the standard sunlight to measure the color reproducibility of camera lenses.

For traditional film cameras, in order to accurately restore the color of an object, the first choice is to choose a film type that has the same color temperature as the light source. Color film can be divided into daylight-type film and light-type film according to color temperature. Daylight-type color film is suitable for shooting under sunlight with a color temperature of about 5500K, and light-type color film is suitable for use under light with a color temperature of 3200-3400K. In addition, the color temperature can also be adjusted through color temperature filters or post-production.

Interesting use of color temperature can create unique works. Many digital cameras now provide a "white balance" function. This function can not only easily restore the color of the subject under different lighting conditions, but also flexibly use this function to adjust the color tone of the picture.

Characteristics of color temperature:

1. In areas with high latitudes, the color temperature is higher and the colors seen are bluish.

2. In low latitude areas, the color temperature is lower and the colors seen are reddish.

3. The color temperature also changes throughout the day. When the sun shines obliquely, more energy is absorbed by clouds and air, so the color temperature is lower. When the sun shines directly, less energy is absorbed, so the color temperature is higher.

4. The sRGB color model of Windows uses 6500 ° K as the standard color temperature, expressed as D65.

5. The color temperature in the early morning is approximately 4400 ° K.

6. The color temperature in the mountains is about 6000 ° K.