What are the differences between the camera's spot metering, average metering (evaluation metering) and central key average metering, and what are their advantages and disadvantages?

Evaluation photometry is to measure the whole picture, that is, to evaluate all the reflected light in the picture. Of course, the light in the central area of the picture will also be taken into account. The advantage of this method is that it is easy to get a balanced picture, and the histogram of the whole picture is balanced, and there will be no local highlight explosion. The disadvantage of evaluation photometry is that it can't meet many conditions, such as shadow, backlight and so on. The principle of spot metering is the same as spot metering, except that the measured area is relatively small (generally around the center 10%). It mixes all the reflected light in a certain area, and then evaluates whether it is more than 18% or less than 18%. The disadvantage is that a very small reference point cannot be measured correctly. The advantage is that it is easier to shoot more realistically and closer to reality when shooting automatically, and there will be no exposure error caused by the wrong spot aiming at the wrong place. Spot metering, as its name implies, only measures one point, which is usually in the same position as the focus (actually only a small area, not a complete point). The advantage of this method is that it can measure a point or object that the photographer thinks is correct according to the photographer's preference, without interference from other nearby lights. For example, it is absolutely necessary to measure your face when you shoot backlight. When taking a photo with large light ratio (for example, half is in the sky and the other half is in the shadow), it is necessary to measure the part that you want to expose correctly. Because the metering point is not necessarily in the center of the composition, or it needs to be re-composed after metering, there is an AE lock, which can lock the exposure when metering is completed. If you don't understand anything, please ask again.