"Every period has its own optical focus." —Laszlo Moholy-Nagy
Using a shallow depth of field in photography results in images in which not all fields (fore-, middle-, and background) are in focus. In a portrait, for example, a sitter might be sharp against a blurred background. This effect may be achieved in analogue photography by adjusting the focus on the camera lens, or in digital photography by incorporating blur effects in post-production.