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Whether it is a mobile phone or a camera, there is a "white balance", which is rarely taken care of when taking pictures. But this does not mean that white balance is useless, it is of great use after understanding.

What is the white balance, how should it be adjusted, and how is it helpful for taking pictures? let's explain it in detail in this article.

White balance A preliminary understanding of white balance can be simply understood as reducing white to white.

If there is a piece of white paper, it is white. But under the light of the colored lights, it changed color. Fortunately, the camera has a white balance, so the white paper is still white.

02, the way white balance works, we all know that the three primary colors of light are red, green and blue, and they can be mixed to produce a variety of colors.

There are three kinds of elements on the camera, which feel the blue, green and red light respectively. In the preset case, the electronic magnification of the three photosensitive circuits is the same, which is the relationship of 1:1:1.

The principle of white balance is to change their magnification. If the current blue, green, and red ratio is 2:1:1, then the white balance will change the magnification to 1:2:2 and eventually revert to white.

White balance and color temperature in physics, the absolute blackbody is heated from absolute zero (- 273 °) and gradually emits red, yellow, white and blue light as the temperature increases.

If the light emitted by the A bulb is the same as that emitted by the absolute blackbody at 2000 °, then the color temperature of the A bulb is 2000 "273" 2273 K.

When the color temperature is very high, the color is blue; when the color temperature is very low, the color is red.

White balance is to make up for color bias, so white balance and color temperature are just the opposite. When the white balance is low, the color of the photo is blue, and when the white balance is high, the color of the photo is red.

Important conclusion

White balance = ambient color temperature, no color bias.

White balance > ambient color temperature, reddish.

White balance < ambient color temperature, blue.

Color temperature and relative color temperature if you follow the color temperature defined by the absolute blackbody, you will find that you can only describe red light, yellow light, white light and blue light. What about the green light and the purple light?

Because of the difference in relative spectral power distribution, the coordinates of a kind of light can not completely coincide with the trajectory of the absolute blackbody, so the color temperature is represented by the nearest absolute blackbody coordinates, which is called "relative color temperature".

For example, in the following picture, although the colors of point An and point B are different, their relative color temperatures are both 10000K.

There are many tutorials that confuse color mildness and relative color temperature, which should be distinguished according to the context when reading.

05. White balance offset White balance when adjusting the color deviation, we should not only find the corresponding relative color temperature, but also know how far the real color temperature is from the relative color temperature, and whether it is shifted to green or magenta, and finally we can make corresponding adjustments.

When you adjust the white balance in the image editing software, you can also see two options, one is called "color temperature", which is used to change the relative color temperature, and the other is called "hue", which is used to change the offset part.

In the menu settings of SLR and micro-single, there is often a "white balance offset" option, which you can adjust manually when turned on.

Different brands of cameras may have different names, so you can find out for yourself if you want to study it. But I don't think this function is useful.

06, various modes of white balance AWB: this is automatic white balance, English automatic white balance acronym, camera automatic adjustment. It is suitable for most cases where the color deviation is not serious.

Preset mode: the camera also provides many presets according to the color of common light, such as cloudy days, tungsten lamps and so on. But lamps and lanterns manufacturers don't care about you, so this model is of little practical significance.

Manual mode (K): here you can manually change the value of the white balance. This doesn't make much sense either, because you can't change the color of the offset.

07, custom white balance if in a warm yellow light, the scenery is yellow, but the automatic white balance does not correct the color deviation.

Why? Because the degree of adjustment of the automatic white balance is limited, the camera does not know whether the yellow in front of the eyes is partial, or whether the scene itself is yellow. In case it is already yellow and I make it white for you, you must not scold me.

At this point, we need to customize the white balance, the principle is to "provide a white to the camera", let the camera "adjust to this standard".

Customize the method of white balance:

1. Take Canon DSLR as an example. In the same light environment, take a picture of pure white (white wall, white paper) to ensure that white fills the whole picture.

two。 Then select Custom White balance from the menu and select the photo you just took as the definition benchmark.

The first special way to play white balance is to change the dim color of the photo.

I want to shoot a piece of bamboo. In the face of the green bamboo, the camera mistakenly thinks that the light at the scene is too green, so it automatically reduces the green, resulting in a dim color of the photo.

After I manually customize the white balance, and then shoot the bamboo, the color of the photo will not be too dim.

Professional mode needs to be turned on on the phone. Take Huawei phone as an example, you can first take a scene against a pure white object (do not shoot), and then press AWB to lock the white balance, and then take photos.

The second is to create a special color bias effect.

If I want to take a bluish picture, I can first take a picture of a yellow (blue complementary color) object and use this photo to customize the white balance. In order to change yellow to white, the camera will automatically add blue, so that the photos taken will be blue.

Of course, you can also manually adjust the K value of the white balance directly, which is easier. For example, when shooting the starry sky, it is usually black, and after adjustment, you can get a blue night sky.

This article is from the official account of Wechat: photography Research Society (ID:shoujiPhotography), author: mobile photography and Photoshop

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