Introduction to Photography Notes _ Understanding Colors

The filter of the camera is Bayer filter.

After obtaining the color from nature, the camera records the information of three primary colors (RGB), and synthesizes the color information of the photo by recording the brightness information of the photosensitive layer of three primary colors. For example, a color photo, we can take out the blue channel separately, and we can see that only the blue brightness information is recorded in it.

Because the camera records the brightness information of three primary colors instead of the colors perceived by human eyes, the camera will convert the brightness information recorded by the camera into the colors perceived by human beings through a series of complicated operation processes. In order to ensure the accuracy of this process, we should balance the color recorded by the camera and the color perceived by human beings. First, we need to know the color temperature and white balance.

Simply put, the color temperature can measure the color of a luminous object. Theoretically, color temperature refers to the color of an absolute blackbody heated from absolute zero (minus 273 degrees). After heating, the black body gradually changes from black to red, yellow and white, and finally emits blue light. Physically speaking, color temperature is just the opposite of our understanding of cool color and warm color. We think that red is a warm color, but the red color temperature is low (about 2000K) and the blue color temperature is high. As shown in the figure below:

The white balance of the camera is to make the photo as close as possible to the actual environmental effect. The white balance of a camera is actually a basic color temperature value. For example, we set the white balance of the camera to 6000K, which actually tells the camera that the basic color temperature value in the current shooting environment is 6000K, and the camera will judge according to this value and get our color. In fact, the camera will use this basic value of color temperature in white balance as the basis for judging white.

The simplest white balance mode is automatic white balance, but sometimes the effect of automatic white balance is not ideal. At this time, you need to manually adjust the white balance. There are two ways:

(1) Use the built-in white balance mode preset by the camera.

Usually there are many modes of white balance, which we can directly correspond to according to the light environment.

(2) Manually modify the color temperature value of the white balance, that is, the k value.

We modify the white balance to get the color atmosphere we want. There are probably two situations as follows:

(1) The current white balance is not accurate enough. By setting the white balance, the color of the current shooting environment can be more truly restored.

For example, in a dark environment, there are lights all around. At this time, the face in the photo may be red or blue. By modifying the white balance, the color of the face in the photo can be closer to the real skin color.

(2) By modifying the white balance, we can get the environment we want.

For example, at sunset, we want to get the golden afterglow of the sun and the red clouds in the sky, but in reality, the photos may be dim and blue, so we need to increase the color temperature value to get warm photos close to the sunset atmosphere.

Also, we want to shoot blues at night, but the sky is not blue enough. At this time, it is necessary to lower the color temperature and make the sky blue.

Influence of white balance parameters on photo effect;

For example, the current color temperature value is 5000. If the color temperature of the camera is higher than 5000, the photo will be red, showing obvious warm tones. If the camera's color temperature value is lower than 5000, the photo will be blue, showing obvious cool tone.

Unlike exposure, once something goes wrong, it is not easy to adjust later (for example, increasing exposure later will increase noise). Color temperature is a good adjustment parameter. When shooting with raw files, you can modify the color temperature later.

When adjusting the color temperature of raw files, there are also settings to adjust the tone of photos. Color temperature adjustment controls the red and blue deviation of photos, while color tone adjustment is generally green and purple. Adjusting these two items at the same time can realize the later adjustment of photo white balance.

Basically, the requirements for color temperature adjustment in night shooting are still relatively high. Therefore, naked-eye shooting should use raw files as much as possible to adjust the white balance later.

The camera has two color modes, ARGB and SRGB. These two modes are different, so we should pay attention to them when adjusting. Normal screen display, we can choose SRGB.

The most commonly used camera style is the photo style of the camera, which will affect the color performance of the photo (including color saturation, brightness, sharpness, contrast, etc. ), thus affecting the impression of the final photo. Therefore, we need to set a suitable photo style and use standard or automatic under normal conditions. Specific to some specific shooting scenes, portrait mode can be used when shooting portraits, and landscape or bright mode can be used when shooting landscapes.

The camera records colors through brightness information of different channels. So in the later adjustment, we are actually adjusting the color relationship between different colors. Therefore, when adjusting colors, not only saturation, but also individual color branches, such as red, blue and green, will be adjusted separately.

Hue: Hue is actually the color of color.

Contrast: Contrast reflects the difference between the brightest and darkest, and histogram is the difference between the two ends of the color scale. The greater the contrast, the greater the difference between light and shade.

Saturation: In fact, it is the purity of color. A saturation of 0 actually means a purity of 0 and no color (black and white photos). The higher the saturation, the closer the color is to solid color.

As shown in the figure below:

Two misunderstandings in adjusting photos: the higher the saturation of photos, the better; The higher the contrast, the better.

The higher the saturation of the photo, the more gorgeous it will be, and the color of the photo will be distorted (because of the excessive color in nature), which is very fake.

If the contrast is too high, the contrast between light and shade of the photo will be particularly large and the photo will look particularly hard.

These two aspects need to be avoided when adjusting photos. Usually, in daily shooting, we need to feel more about the colors in nature and explore the appropriate forms of color expression, so that our photos can get real color beauty.