What defines depth of field in photography?

Depth of field in photography refers to the range of distance within a scene that appears acceptably sharp in an image. It is determined by the focus area between the nearest and furthest objects that are in focus. When you adjust your camera settings, such as aperture, focal length, and distance from the subject, you alter the depth of field, allowing either a shallow depth of field (where subject focus is clear and the background is blurred) or a deep depth of field (where multiple elements in the foreground and background are in focus).

In contrast, the other options address different aspects of photography. The overall brightness of an image relates to exposure, which is influenced by the combination of shutter speed, aperture, and ISO settings, but doesn't define depth of field. The proportion of light let in through the lens, while crucial for exposure, does not directly correlate to depth of field. Lastly, the angle of view captured by the lens pertains to the field of view of the camera and how much of the scene is captured, which is separate from the concept of depth of field.