Traditional Culture Encyclopedia - Photography major - What is a grey card?

What is a grey card?

A grayscale image is a monochrome image with 256 grayscale color gamut or levels from black to white. Each pixel in the image is represented by 8-bit data, so the pixel value is one of 256 gray levels between black and white. The image is only gray, and there is no color change. In Photoshop, grayscale images are regarded as digital images of color channels.