White balance is a very important concept in the field of TV camera, through which it can solve a series of problems of color reproduction and tone processing. White balance is produced with the true color reproduction of electronic images. White balance was applied earlier in the field of professional photography. It is now widely used in household electronic products (home video cameras, digital cameras). It has become more and more simple and easy, but many users still do not understand the working principle of white balance, and there are many misunderstandings in understanding.
1. What is white balance
White balance, literally understood as white balance. What is white? This involves some knowledge of chromatics. White refers to the visual response formed by the light reflected into the human eye due to the same proportion of blue, green, and red colors and a certain brightness. We all know that white light is composed of seven colors of red, orange, yellow, green, cyan, blue, and purple. These seven colors are formed by mixing three primary colors of red, green, and blue in different proportions. When the proportions of the three primary colors in the composition are the same, people traditionally call it achromatic, and the light reflected by black, white, gray, gold, and silver is achromatic. Popular understanding of white is the brightness that does not contain color components. The white or other colors seen by the human eye are related to many factors such as the intrinsic color of the object itself, the color temperature of the light source, the reflection or transmission characteristics of the object, and the visual perception of the human eye (please refer to "Principles of Colorology"). For example, when the colored light is irradiated to the achromatic object, the color of the reflected light of the object is the same as the color of the incident light, that is, the white object is red when the red light is irradiated, and when the two or more colored lights are irradiated to the achromatic object at the same time, the object color is The additive color effect, such as red light and green light illuminating a white object at the same time, the object appears yellow. When the colored light shines on the colored object, the color of the object shows the subtractive effect. For example, a yellow object appears red when illuminated by magenta light, green when illuminated by cyan light, and gray or black when illuminated by blue light.
Before understanding white balance, we must understand another very important concept-color temperature. The so-called color temperature, in short, is to quantitatively express the color in Kelvin temperature (K). The famous British physicist Kelvin believes that if a black body material can absorb all the heat falling on it without loss, and at the same time can release all the energy generated by the heat in the form of "light", it will Will change to different colors due to the level of heat. For example, when the blackbody receives a thermal force equivalent to 500-550 degrees Celsius, it will become dark red, and when it reaches 1050-1150 degrees Celsius, it will become yellow, and the temperature will continue to rise to blue. The color component of the light source is corresponding to the thermal temperature of the black body. The color temperature of any light is equivalent to the "temperature" that the black body emits when it emits the same color. This temperature is used to express the characteristics of a certain color. To distinguish the others, this is the color temperature. During the ironing process, the black iron gradually turns red at the furnace temperature, which is the best example of the blackbody theory. The phenomenon of color temperature is very common in daily life, I believe people are not new to it. The light emitted by the tungsten filament lamp is yellowish due to the low color temperature. Different street lamps will also emit different colors of light. The flame of natural gas is blue because the color temperature is higher. The color temperature of the cloudless blue sky is about 10000 K, the cloudy day is about 7000 ~ 9000 K, the color temperature under sunny direct sunlight is about 6000 K, the color temperature at sunrise or sunset is about 2000 K, and the color temperature of candlelight is about 1000 K. At this time, it is not difficult to find a rule: the higher the color temperature, the bluer the light color; the lower the color temperature, the redder. When the color temperature of a certain color light is higher than other color lights, it means that the color light is bluer than other color lights, and vice versa. It is also reddish; similarly, when a color light is bluer than other color lights, it means that the color temperature of the color light is higher, but vice versa.
Due to the unique adaptability of the human eye, sometimes we can not find the change in color temperature. For example, if you have been under a tungsten lamp for a long time, you will not feel that the white paper under the tungsten lamp is reddish. If you suddenly change the fluorescent lamp to a tungsten lamp, you will find that the color of the white paper is reddish, but this This feeling can only last for a while. The CCD of the camera is not as adaptable as the human eye, so if the color adjustment of the camera is inconsistent with the color temperature of the scene lighting, color cast will occur. So what is white balance? White balance is to adjust the color circuit inside the camera to offset the color cast under different color temperature conditions, which is closer to the visual habit of the human eye. White balance can be simply understood as that under any color temperature condition, the standard white shot by the camera lens is adjusted by the circuit to make it still white after imaging. This is a common occurrence, but not all. White balance is actually adjusted by the internal circuit of the camera (changing the balance between the three CCD levels of blue, green, and red) so that the light reflected into the lens appears to be eliminated. color. If the white balance is adjusted with reddish color light, the image of that color light will be achromatic, and the scenes of other colors will be bluish (complementary color relationship).
Second, the working principle of white balance
White balance is a very abstract concept. The most popular understanding is to make the image made of white still white. If white is white, the images of other scenes will be close to the color vision habits of the human eye. The process of adjusting the white balance is called white balance adjustment. There are generally three ways to adjust the white balance in the previous equipment: preset white balance, manual white balance adjustment, and automatic tracking white balance adjustment. Normally, according to the white balance adjustment procedure, the white balance adjustment switch is pushed, the white balance adjustment circuit starts to work, automatically completes the adjustment work, and records the adjustment result. If you master the working principle of white balance, it will be more targeted and handy.
White balance works like this: There are three CCD electronic coupling elements inside the camera, they feel the blue, green and red light respectively. Under the preset condition, the electronic amplification ratio of the three photosensitive circuits is the same, which is 1: 1: In relation to 1, the adjustment of white balance changes this proportional relationship according to the scene being adjusted. For example, the ratio of the blue, green, and red light of the adjusted scene is 2: 1: 1 (the proportion of blue light is high, and the color temperature is high), then the ratio of the white balance after adjustment is 1: 2: 2, the adjusted circuit In the magnification ratio, the proportion of obvious blue is reduced, and the proportion of green and red is increased. In this way, the proportion of blue, green, and red will be the same after the adjusted scene passes the white balance adjustment circuit to the captured image. That is to say, if the adjusted white is a little blue, then the white balance adjustment will change the normal proportional relationship and weaken the amplification of the blue circuit, while increasing the ratio of green and red, so that the resulting image is still white.
To change the way to consider the problem of white balance adjustment, the camera will not "reject" the adjusted scene placed in front of the lens within the white balance adjustment tolerance, which means that the lens can adjust the white balance against any scene. In most cases, the white-adjustable whiteboard (card) is used to adjust the white balance, because the white-adjustable whiteboard (card) can most effectively reflect the color temperature of the environment. In fact, in many circumstances, the whiteboard (card) is not white. It is less likely to be a bit blue or other colors, and experienced cameras will also use the blue sky to adjust the white balance to get a reddish-yellow tone. After figuring out how white balance works, you will boldly try different effects when you use it again, which enriches the camera creation.
3. White balance adjustment
The color temperature of daylight is constantly changing in life. It can be said that no two places have the same color temperature. Different regions, seasons, ground conditions, weather, morning and evening, etc. will affect the color temperature, and there are a lot of artificial light sources. The color temperature is also different. There are three methods for the cameraman to adjust the white balance: coarse adjustment, fine adjustment and automatic tracking (ATW). Coarse adjustment refers to changing the color temperature filter under preset conditions to make the color temperature close to the factory setting of 3200K; fine adjustment is Refers to the camera's white balance adjustment function in conjunction with the color temperature filter to obtain a more accurate adjustment result for the specific environment color temperature; automatic tracking refers to the automatic tracking function (ATW) of the camera, the camera itself changes according to the color temperature of the picture Adjust at any time.
The preset function is the blue, green, and red light balance set by the camera with a color temperature of 3200K. When the ambient color temperature is 3200K, the camera color temperature filter is placed at 3200K, the scene can get the correct color reproduction; when the ambient color temperature is 5600K, the camera color temperature filter is placed at 5600K, the scene can get the correct color reproduction. When the ambient color temperature is in the range of 32000K up to 1000K and 5600K up and down 1000K, the white balance preset function can be used to obtain a color reproduction acceptable to the human eye. Because the color temperature deviation is not large, the captured picture shows subtle color changes. This has the advantage that different living environments will have different color tones due to the influence of environmental colors and lighting differences. If you adjust white everywhere, the different environments will show the effect of a single white light illumination, and the use of white balance presets can preserve this A rich variety of colors.
The general method of fine whitening is to adjust the white balance in the shooting environment by adjusting the whiteboard (card) along the shooting direction. This is a common situation, and there are several very flexible methods for fine whitening. Use a standard whiteboard with good permeability, place it in front of the lens, and adjust the white balance in the shooting environment to the light source illumination direction or the main shooting direction. A professional camera will give a color temperature reading. For example, 5000K, if you want to shoot to restore normal pictures, shoot with this white balance result. In camera creation, sometimes you want to get a picture with color deviation to achieve the purpose of creation. At this time, you can use any scene to adjust the white balance. The color temperature of the adjusted white scene has a complementary color relationship with the color deviation of the picture. Cyan, the white screen with green tones is biased toward magenta, and the white screen with blue tones is biased toward yellow. The white balance automatic tracking function (ATW) is adjusted in real time as the color temperature of the scene taken by the lens changes. If a push lens or a pan is moved due to the color temperature of the scene taken (the color temperature of the scene taken by the lens is different from the color temperature of the ambient lighting) Changes will cause the color of the picture to change within a lens. For example, if the lens is pushed from the person's panorama to the face close-up, the color temperature of the lens will be different due to changes in the scene, and the skin color of the person in the picture will also change, so this mode is not recommended for non-special cases.
1. What is white balance
White balance, literally understood as white balance. What is white? This involves some knowledge of chromatics. White refers to the visual response formed by the light reflected into the human eye due to the same proportion of blue, green, and red colors and a certain brightness. We all know that white light is composed of seven colors of red, orange, yellow, green, cyan, blue, and purple. These seven colors are formed by mixing three primary colors of red, green, and blue in different proportions. When the proportions of the three primary colors in the composition are the same, people traditionally call it achromatic, and the light reflected by black, white, gray, gold, and silver is achromatic. Popular understanding of white is the brightness that does not contain color components. The white or other colors seen by the human eye are related to many factors such as the intrinsic color of the object itself, the color temperature of the light source, the reflection or transmission characteristics of the object, and the visual perception of the human eye (please refer to "Principles of Colorology"). For example, when the colored light is irradiated to the achromatic object, the color of the reflected light of the object is the same as the color of the incident light, that is, the white object is red when the red light is irradiated, and when the two or more colored lights are irradiated to the achromatic object at the same time, the object color is The additive color effect, such as red light and green light illuminating a white object at the same time, the object appears yellow. When the colored light shines on the colored object, the color of the object shows the subtractive effect. For example, a yellow object appears red when illuminated by magenta light, green when illuminated by cyan light, and gray or black when illuminated by blue light.
Before understanding white balance, we must understand another very important concept-color temperature. The so-called color temperature, in short, is to quantitatively express the color in Kelvin temperature (K). The famous British physicist Kelvin believes that if a black body material can absorb all the heat falling on it without loss, and at the same time can release all the energy generated by the heat in the form of "light", it will Will change to different colors due to the level of heat. For example, when the blackbody receives a thermal force equivalent to 500-550 degrees Celsius, it will become dark red, and when it reaches 1050-1150 degrees Celsius, it will become yellow, and the temperature will continue to rise to blue. The color component of the light source is corresponding to the thermal temperature of the black body. The color temperature of any light is equivalent to the "temperature" that the black body emits when it emits the same color. This temperature is used to express the characteristics of a certain color. To distinguish the others, this is the color temperature. During the ironing process, the black iron gradually turns red at the furnace temperature, which is the best example of the blackbody theory. The phenomenon of color temperature is very common in daily life, I believe people are not new to it. The light emitted by the tungsten filament lamp is yellowish due to the low color temperature. Different street lamps will also emit different colors of light. The flame of natural gas is blue because the color temperature is higher. The color temperature of the cloudless blue sky is about 10000 K, the cloudy day is about 7000 ~ 9000 K, the color temperature under sunny direct sunlight is about 6000 K, the color temperature at sunrise or sunset is about 2000 K, and the color temperature of candlelight is about 1000 K. At this time, it is not difficult to find a rule: the higher the color temperature, the bluer the light color; the lower the color temperature, the redder. When the color temperature of a certain color light is higher than other color lights, it means that the color light is bluer than other color lights, and vice versa. It is also reddish; similarly, when a color light is bluer than other color lights, it means that the color temperature of the color light is higher, but vice versa.
Due to the unique adaptability of the human eye, sometimes we can not find the change in color temperature. For example, if you have been under a tungsten lamp for a long time, you will not feel that the white paper under the tungsten lamp is reddish. If you suddenly change the fluorescent lamp to a tungsten lamp, you will find that the color of the white paper is reddish, but this This feeling can only last for a while. The CCD of the camera is not as adaptable as the human eye, so if the color adjustment of the camera is inconsistent with the color temperature of the scene lighting, color cast will occur. So what is white balance? White balance is to adjust the color circuit inside the camera to offset the color cast under different color temperature conditions, which is closer to the visual habit of the human eye. White balance can be simply understood as that under any color temperature condition, the standard white shot by the camera lens is adjusted by the circuit to make it still white after imaging. This is a common occurrence, but not all. White balance is actually adjusted by the internal circuit of the camera (changing the balance between the three CCD levels of blue, green, and red) so that the light reflected into the lens appears to be eliminated. color. If the white balance is adjusted with reddish color light, the image of that color light will be achromatic, and the scenes of other colors will be bluish (complementary color relationship).
Second, the working principle of white balance
White balance is a very abstract concept. The most popular understanding is to make the image made of white still white. If white is white, the images of other scenes will be close to the color vision habits of the human eye. The process of adjusting the white balance is called white balance adjustment. There are generally three ways to adjust the white balance in the previous equipment: preset white balance, manual white balance adjustment, and automatic tracking white balance adjustment. Normally, according to the white balance adjustment procedure, the white balance adjustment switch is pushed, the white balance adjustment circuit starts to work, automatically completes the adjustment work, and records the adjustment result. If you master the working principle of white balance, it will be more targeted and handy.
White balance works like this: There are three CCD electronic coupling elements inside the camera, they feel the blue, green and red light respectively. Under the preset condition, the electronic amplification ratio of the three photosensitive circuits is the same, which is 1: 1: In relation to 1, the adjustment of white balance changes this proportional relationship according to the scene being adjusted. For example, the ratio of the blue, green, and red light of the adjusted scene is 2: 1: 1 (the proportion of blue light is high, and the color temperature is high), then the ratio of the white balance after adjustment is 1: 2: 2, the adjusted circuit In the magnification ratio, the proportion of obvious blue is reduced, and the proportion of green and red is increased. In this way, the proportion of blue, green, and red will be the same after the adjusted scene passes the white balance adjustment circuit to the captured image. That is to say, if the adjusted white is a little blue, then the white balance adjustment will change the normal proportional relationship and weaken the amplification of the blue circuit, while increasing the ratio of green and red, so that the resulting image is still white.
To change the way to consider the problem of white balance adjustment, the camera will not "reject" the adjusted scene placed in front of the lens within the white balance adjustment tolerance, which means that the lens can adjust the white balance against any scene. In most cases, the white-adjustable whiteboard (card) is used to adjust the white balance, because the white-adjustable whiteboard (card) can most effectively reflect the color temperature of the environment. In fact, in many circumstances, the whiteboard (card) is not white. It is less likely to be a bit blue or other colors, and experienced cameras will also use the blue sky to adjust the white balance to get a reddish-yellow tone. After figuring out how white balance works, you will boldly try different effects when you use it again, which enriches the camera creation.
3. White balance adjustment
The color temperature of daylight is constantly changing in life. It can be said that no two places have the same color temperature. Different regions, seasons, ground conditions, weather, morning and evening, etc. will affect the color temperature, and there are a lot of artificial light sources. The color temperature is also different. There are three methods for the cameraman to adjust the white balance: coarse adjustment, fine adjustment and automatic tracking (ATW). Coarse adjustment refers to changing the color temperature filter under preset conditions to make the color temperature close to the factory setting of 3200K; fine adjustment is Refers to the camera's white balance adjustment function in conjunction with the color temperature filter to obtain a more accurate adjustment result for the specific environment color temperature; automatic tracking refers to the automatic tracking function (ATW) of the camera, the camera itself changes according to the color temperature of the picture Adjust at any time.
The preset function is the blue, green, and red light balance set by the camera with a color temperature of 3200K. When the ambient color temperature is 3200K, the camera color temperature filter is placed at 3200K, the scene can get the correct color reproduction; when the ambient color temperature is 5600K, the camera color temperature filter is placed at 5600K, the scene can get the correct color reproduction. When the ambient color temperature is in the range of 32000K up to 1000K and 5600K up and down 1000K, the white balance preset function can be used to obtain a color reproduction acceptable to the human eye. Because the color temperature deviation is not large, the captured picture shows subtle color changes. This has the advantage that different living environments will have different color tones due to the influence of environmental colors and lighting differences. If you adjust white everywhere, the different environments will show the effect of a single white light illumination, and the use of white balance presets can preserve this A rich variety of colors.
The general method of fine whitening is to adjust the white balance in the shooting environment by adjusting the whiteboard (card) along the shooting direction. This is a common situation, and there are several very flexible methods for fine whitening. Use a standard whiteboard with good permeability, place it in front of the lens, and adjust the white balance in the shooting environment to the light source illumination direction or the main shooting direction. A professional camera will give a color temperature reading. For example, 5000K, if you want to shoot to restore normal pictures, shoot with this white balance result. In camera creation, sometimes you want to get a picture with color deviation to achieve the purpose of creation. At this time, you can use any scene to adjust the white balance. The color temperature of the adjusted white scene has a complementary color relationship with the color deviation of the picture. Cyan, the white screen with green tones is biased toward magenta, and the white screen with blue tones is biased toward yellow. The white balance automatic tracking function (ATW) is adjusted in real time as the color temperature of the scene taken by the lens changes. If a push lens or a pan is moved due to the color temperature of the scene taken (the color temperature of the scene taken by the lens is different from the color temperature of the ambient lighting) Changes will cause the color of the picture to change within a lens. For example, if the lens is pushed from the person's panorama to the face close-up, the color temperature of the lens will be different due to changes in the scene, and the skin color of the person in the picture will also change, so this mode is not recommended for non-special cases.
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