Certified Professional Photographer (CPP) Practice Exam

Which factor, combined with f-stop and camera-to-subject distance, controls the depth of field?

1. Shutter speed

2. Lens aperture

3. Focal length

4. ISO setting

The correct answer is: Focal length

The correct factor that, when combined with f-stop and camera-to-subject distance, controls the depth of field is the focal length. The focal length of a lens significantly influences how much of the scene appears in focus both in front of and behind the subject. In photography, a longer focal length results in a shallower depth of field, meaning that only a narrow slice of the scene will be in focus, while the areas in front of and behind the subject will be more blurred. This is often desirable in portrait photography, where the subject is isolated from the background. Conversely, a shorter focal length typically produces a deeper depth of field, allowing more of the scene to be sharp and in focus, which is beneficial for landscape photography where clarity throughout is desired. While f-stop and camera-to-subject distance also play roles in depth of field control, it is the relationship with focal length that has a distinct effect on how depth of field is visualized in the final image.