What is a gradient filter, its effect and usage.

Gradient grey mirror (short for gradient change-gray) is a kind of filter and belongs to gradient mirror. Also known as GND mirror or medium gray gradient mirror. Gradient grey mirror is generally used when shooting scenery with large contrast, and its function is to make the light ratio of light and dark parts within a controllable range, thus ensuring correct exposure and post-production.

There are two kinds of gradient mirrors: rectangular and circular. Half is gray and half is colorless, so it can reduce part of the exposure in the picture and change the contrast of the photo. From the form of gradient, it can be divided into soft gradient and hard gradient. "Soft" refers to excessive extent, and vice versa.

Usually, when taking landscape photos with the sky as the background, the exposure (EV value) between the sky and the ground is different by several levels of aperture, either the sky is overexposed or the ground is underexposed, with no details. Gradual grey mirror can effectively solve this problem. By adjusting the direction of color change distribution through the rotation of the lens, the gray part is blocked in the sky, which reduces the brightness of the sky, balances the exposure difference between the sky and the ground, and highlights the details of the cloud.