How many kinds of filters are there? What's the role?

There are many kinds of filters, or color filters, and there are three kinds commonly used in landscape photography.

UV mirror, function: cheap, many people use it to protect their lenses. In fact, its main function is to filter out the ultraviolet rays in the scenery and make it look more comfortable.

Polarizer, function: glare and reflection often appear when taking pictures, which reduces the color saturation of the scene and even makes it impossible to see the object clearly. Polarizers can be a good solution. For example, when you shoot the water surface, you can eliminate the reflection from the water surface, and when you shoot the blue sky and white clouds, you can make the sky bluer and white clouds richer. In addition, the polarizer can also weaken the intensity of light entering the lens and reduce the shutter speed.

Grey mirror, function: weaken the light intensity and slow down the shutter speed, especially when the light is strong, you can use a slower shutter speed. In addition, when shooting scenery such as sunset glow, the contrast between the sky and the ground is large, and the ground will lose details when exposed according to the sky. On the contrary, the sky will lose its details. At this time, a gray gradient mirror can be used to solve this problem.