Which of the following is NOT a primary method to control depth of field?

• A. Focal length of lens
• B. Aperture
• C. ISO sensitivity
• D. Camera to subject distance

Answer: (C)

Depth of field is shaped by three main controls: aperture, focal length, and how close you are to the subject. A smaller aperture (higher f-number) increases depth of field, bringing more of the scene into sharp focus. A longer lens or being closer to the subject tends to shrink depth of field, creating a blurrier background, while using a shorter focal length or stepping farther away increases the range that remains sharp. ISO, the sensor’s sensitivity to light, does not directly change the depth of field; it only affects exposure and noise. You can raise ISO to compensate for exposure when you adjust other settings, but the amount of blur in front of and behind the plane of focus—i.e., the depth of field—remains governed by aperture, focal length, and subject distance.