This paper lists how to deal with the relationship between light and background when taking high-profile and low-profile portrait photos.

If you shoot a high-profile portrait, the background light intensity is more than 2 levels higher than the person's light intensity. Dark-tone portraits are just the opposite, and the background light is weaker than the light of the characters by more than two grades. However, the difference between the second gear and above here is not that the bigger the better, the better to have details. That is, there is white in white and black in black. It's not black or white.