Use of photographic gray card

The following is a brief introduction: put the gray board at the position of the subject, so that the light (natural light or artificial light) comes from the same direction as the digital camera, set the white balance at the manual white balance position, and select the calibration function, adjust the focus ring to infinity facing the gray board, adjust the distance or zoom to make the gray board occupy the whole screen, press the shutter to shoot the out-of-focus picture, and select OK to get the real white balance ... for reference only.