Shallow depth of field means to have a small amount of the image in focus.

When we talk about the main characteristics of depth of field, we usually classify it into two categories, shallow depth of field and deep depth of field.

When the aperture is large (ex. f/1.8), the area in front and behind the focus point is very slim or shallow. That means that objects right in front and right behind the plane of focus is already going out of focus.

Shallow depth of field is used primarily to isolate the subject from its environment, and it is used a lot in portrait work, macro photography, and sports photography.