What is color temperature
Color temperature, as the name implies, can be understood as the temperature of light. Intuitively, the low color temperature light source is reddish, called "warm light"; the high color temperature light source is bluer, called "cold light".
The color change from low color temperature to high color temperature is red-orange red-yellow-yellow-white-white-blue and white.
The color temperature unit is Kelvin (K). The measurement method is to heat an absolute black body from 0 Kelvin. When the radiation of the black body is the same as the radiation of the light source in the visible light region, the temperature of the black body is the color temperature of the light source.
Various types of light are seen in daily life. The usual color temperature is: standard candle light is 1930K; tungsten lamp is 2760-2900K; fluorescent lamp is 3000K; flash is 3800K; noon sunlight is 5600K; electronic flash is 6000K, etc. , Are basically between 2000 and 10000K.
Generally, light below 3300K is called warm light, such as candlelight, which has more red components, giving people a warm, comfortable and warm feeling; light from 3300K to 5300K is called neutral light, such as daylight at noon, the light is softer, giving People feel pleasant and serene; light above 5300K is called cold light, like light on a cloudy day, giving people a bright and cold feeling.
White balance
White balance, which tells the camera what is white
The human visual system has high accuracy in color recognition and can recognize white objects most of the time. The camera's sensor is far inferior to the human eye, and the automatic recognition is very poor. If the deviation from the neutral color temperature is large, the color cast will occur, so you need to select the mode or manually set the color temperature.
The principle of white balance correction is "add red/blue". For example, when the ambient color temperature is 3000K, the white balance of the camera is set to 3000K, and the correct color will be obtained. If the white balance is set to 5000K, the camera will add red to make the image reddish; if the white balance is set to 2000K, the camera will add blue to make the image bluish.
Usually white balance has a variety of scene modes, including auto, tungsten light, fluorescent light, daylight, flash, cloudy, shadow and so on. The effective recognition range of the camera's automatic white balance is 4000-7000K. Generally, automatic white balance is more accurate, but when the ambient color temperature deviates from the neutral color temperature more, you need to accurately adjust the color temperature through the scene white balance, and sometimes even manual white balance is required .
The color cast of the picture is not determined unilaterally by the camera, but is determined by the deviation between the camera's set color temperature and the ambient color temperature. The greater the deviation, the more serious the color cast.
How to correct white balance
The best way to correct white balance is to use 18% gray card in the early stage. Because it is very difficult to accurately determine the color temperature of the environment, you can use the RAW format to shoot an 18% gray card, and then shoot the photos you want to take normally, and then correct it in the post software to get an accurate white balance.
supplement
1. Sometimes the accurate white balance is not necessarily the desired white balance. The proper color cast can bring out the atmosphere that the author wants. For example, the warm atmosphere created by candlelight, and the cyanish color of Japanese photography.
2. The color temperature involves only one value, the thermodynamic temperature scale K, while the white balance involves three values of red, green and blue.
3. Under complex light sources, there will often be different color temperatures of multiple light sources. At this time, the color temperature of the main light source needs to be set.
4. If the color rendering of the previous light source is poor, such as a sodium lamp, the correct white balance cannot be obtained by any means because the spectrum is missing. Therefore, in the shooting with high requirements for white balance, it is necessary to choose a light source with high color rendering.