What is the meaning of No.4 gradient gray background for photography, and how to call No.4 gradient gray in PS?

No.4 gradient gray refers to the gradient between No.4 gray and pure white.

the color code of No.4 ash is #666666, which refers to the colors with RGB of 12 respectively. When picking the color, just enter 666666 or fill in 4 in the red box.

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

Extended data

Gray has positive and negative meanings. "Gray matter" will be associated with IQ and brain power. However, it seems that there are many derogatory terms of gray, and "gray" itself is used to describe some dim and monotonous things, such as gray areas, Cinderella, frustration and so on. There are often all gray suits in the company.

it's hard to make a serious mistake when using gray. It seems to go with any color. Because of its neutrality, it is often used as the background color. It can make other colors stand out.

Baidu Encyclopedia-Gray

Baidu Encyclopedia-Gradient Gray Filter