What function does the "depth of field preview" serve on a camera?

The depth of field preview function on a camera is designed to help photographers visualize the expected depth of field in their images before taking the shot. When this feature is activated, the camera stops down the lens to the selected aperture, allowing the photographer to see which parts of the scene will be in focus and which parts will be out of focus. This is particularly useful because depth of field can significantly affect the composition and storytelling in a photograph, enabling the photographer to make informed decisions about focus, aperture settings, and overall artistic intent.

Understanding how depth of field works is essential for creating the desired effect in photography. For instance, a shallow depth of field might isolate a subject against a beautifully blurred background, while a deep depth of field could keep both foreground and background elements sharp, suitable for landscapes or group shots. The preview serves as a practical tool to assess these outcomes clearly in real-time.