How to choose or use background in portrait photography

In portrait photography, there are various backgrounds, such as plane, depth, indoor and outdoor ... How to depict the subject's personality and highlight the theme through the background can be considered from the following aspects: When a photographer chooses a background according to the theme that the photo wants to clarify, there is usually a very clear creative theme. Because of the different themes, the photographer should make a reasonable choice according to the specific situation. Choose different apertures according to the content of the background. There is no regulation on how much position the background should occupy in the picture, but you can refer to some principles.