Living in the era of fast consumer consumption, while the development of society is moving towards a high speed, people’s activity time in the light is also gradually increasing. Different light sources and light environments will have a great impact on people’s spatial perception, behavior pattern, social activities, physical and mental health.
Next, we’ll look at the color temperature of autofocus cameras and how it affects people and machines.
01 Color temperature
Color temperature is a measure of how much color a light contains. Theoretically, blackbody temperature refers to the absolute blackbody temperature from absolute zero (-273℃) after the color.
As shown in the figure below, when the black body is heated, its color gradually changes from black to red, yellow, white, and finally blue. When heated to a certain temperature, the spectral component of the light emitted by the black body is called the color temperature at this temperature and is measured in “K” (Kelvin).
< Color temperature Image 1- image from the web >
The color temperature of the light source is different, the color of the light will be different, and the visual impact and visual feeling will be very different. (The higher the color temperature, the lower the visual effects).
< Color temperature Image 2- Image from the Web >
02 Color constancy
In the process of acquiring images in human vision, not only the retina is involved, but more importantly, the brain is involved. Vision is an important means for human to acquire external information, and the brain has already helped us establish complex perception and response.
Therefore, there is a physiological mechanism that helps people automatically correct their perception of objects when exposed to light at different color temperatures. This is called color constancy.
< Color temperature yellowish – image from web >
Color constancy: Color constancy:
It refers to the perceptual property that when the color light irradiating the surface of an object changes, the surface color of the object received by people is different, but the perception of the surface color of the object remains unchanged.
For example, white is the natural color of the outer layer of dessert. However, under the irradiation of yellow light source, the outer layer of dessert seen by human eyes will be yellow, but people’s cognition of the outer layer of dessert is still “white”, which is color constancy.
03 White balance
Different from human eyes, cameras do not possess the perceptual characteristics of “color constancy”. Cameras will collect images of different colors as the color of light source changes. Therefore, similar functions need to be added manually, which is called “white balance”.
In the process of color conversion, different white points are specified according to the condition of the light source, so as to obtain the corresponding correct color conversion results and minimize the influence of the light source color on the surface color of the object.
As shown in the figure below, it is assumed that Figure 1 is the image collected under normal light environment and Figure 2 is the image collected under blue light, so the overall picture will be bluer and cooler than Figure 1.
< Figure 1- Normal light environment >
< Figure 2- Overall blue color >
From Figure 1 and Figure 2, it is obvious that there is a certain color difference between the two sides. So if you want to restore Figure 2 to Figure 1, the blue light as an interference factor needs to be “color restored”.
Then the camera will select a point as the white balance point (such as a white headset), and then calculate the “color temperature” of picture 2, so as to “color difference compensation”, and effectively restore picture 1.
< A comparison of the situation in Figure 1 and Figure 2, where is the color difference between different color temperatures >
Simply understood, white balance is used to restore the color of the image.
04 Why does the white Balance matter?
The more “real” the image, the easier it is for people to understand the nature of the thing, and the more sensory impact they can get.
In practical application, the color of light source is not invariable, but changes at any time. For example, the midday sun is a dazzling golden yellow, and the evening sun is orange red. Like neon lights in the city, red, green, blue…
Therefore, the changeable light environment makes the camera face many challenges when collecting images, and the “white balance” function is to quickly adapt to the fast and changeable light and color environment, and try to restore the real image color.
Otherwise, the image quality is not uniform up and down, and people will have a big wrong cognition of the things on the image.
< Different color temperature, visual experience is different – image from web >
In some cases, the “white balance function” also allows people to see things correctly in severely biased environments.
For example, the current environment is heavily red, so people can adjust the color temperature of the camera, slowly eliminate the influence of color, so as to better identify the object itself.
< When Wang Gong developed a dental field camera, he needed to slowly adjust the light color >