Under what circumstances is a small depth of field mostly used in photography?

A large aperture means a small depth of field... For portraits and still life, as long as the background needs to be blurred to highlight the subject, a small depth of field must be used. A small aperture produces a large depth of field. Generally, photos with a wide field of view, portraits in landscapes, some news or documentary subjects, etc. that require photos to contain more information require a large depth of field. When using methods such as snapshots and candid shots, you need to use the hyperfocal distance shooting method, which also requires a small aperture, which also produces a very large depth of field.