When shooting something with a white background using a SLR camera, the background turns gray.

The camera's metering is based on 18% neutral gray. If the screen has a large area of ??white and black, the machine will make an error, and the white will be restored to gray, and the black will be reduced. Restored to gray. Therefore, there is a law of white plus black minus in photography.

For such a large area of ??white, you need to use exposure compensation, just add one or two stops.

If it is black, reduce the exposure.

This has nothing to do with white balance, just set it to automatic. If the color is off, correct the exposure first and then adjust the white balance.

This is the same as taking pictures of snow scenes. If you press the meter of the machine, the snow scene will be gray.