Final answer:
Depth of Field is controlled by the aperture. A wide aperture creates a shallow depth of field with a blurry background, while a small aperture leads to a larger depth of field with both foreground and background in focus. Shutter speed and ISO do not directly control depth of field.
Step-by-step explanation:
Depth of Field is controlled primarily by the aperture of the camera. Aperture is the round hole within the lens that allows light to reach the sensor. The size of the aperture determines how much light enters the camera and the resulting depth of field. A wide-open aperture results in a shallow depth of field, making the subject in focus while the background appears blurry. Conversely, a small aperture ensures a large depth of field, where both the foreground and background of the image appear in focus. Shutter speed and ISO are parts of the exposure triangle along with aperture; however, they do not control depth of field directly. Shutter speed affects how motion is captured, and ISO affects the sensitivity of the camera's sensor to light. Manual and semi-manual shooting modes, such as Shutter Priority (S or TV) and Aperture Priority (A or AV), allow photographers to control either shutter speed or aperture to achieve the desired exposure and effect, but for depth of field specifically, it's the aperture that's the controlling factor.