Snow looks clean, but why do people say it is dirty?

What is the hottest photography theme in winter? It's nothing more than shooting snow scenes. Although the snow scene is beautiful, the snow scenes taken by many people are not very beautiful, especially it looks dark and has no actual white light. What is the reason? This situation is actually caused by your failure to master the law of "white plus black minus". Many novice photographers often find it difficult to understand "white plus black minus" and think that the scene is already so white. Wouldn't it be too white to add exposure compensation operation? Or the scene is already dark. If you reduce the exposure compensation operation, isn't it getting darker and darker? This is just our logical understanding, but the camera is different from our logical understanding.

Let's do an experiment first to understand the "idea" of the camera. Take a picture of pure black and a picture of pure white paper with the camera. We will be surprised to find that both photos are gray, which does not mean that the black and white colors are the same, because the camera calculates the exposure by collecting the reflected light of the object, and different objects have different reflective abilities to light. The camera is not smart enough to judge the amount of light reflected by each object, so a standard must be set artificially. A long time ago, scientists found that the average reflectivity of natural objects was 18%, so they set the photometric standard of the camera as 18%, which is what we often call 18 degrees. That is, no matter whether white paper or black paper is photographed by automatic photometry, the result is gray. This situation requires manual judgment and intervention. In order to restore the original white color of white paper (such as shooting snow), it is necessary to increase the exposure compensation, and in order to restore the original black color of black paper (such as shooting coal), it is necessary to reduce the exposure compensation.

When you shoot a bright object, such as snow, the camera will mistakenly think that the environment is bright, thus automatically reducing the exposure, but in fact it will lead to underexposure, so that the snow will turn gray. When shooting dark objects, the camera will think that the environment is dark, so it will automatically increase the exposure. Therefore, due to the increase of exposure, black is no longer so black and becomes gray. Seeing this, everyone should understand the law of "white plus black minus". In order to keep the snow photos white, it is necessary to add 1-2 exposure compensation on the basis of normal exposure to restore the original color of the snow scene.