Certified Professional Photographer (CPP) Practice Exam

What happens to the depth of field as the lens opening decreases?

1. It increases

2. It remains constant

3. It decreases

4. It becomes unpredictable

The correct answer is: It increases

When the lens opening, or aperture, decreases, the depth of field increases. Depth of field refers to the range within a photograph that appears acceptably sharp. A smaller aperture (larger f-stop number) allows less light to hit the sensor and increases the distance from the foreground to the background that remains in focus. This occurs because a smaller aperture creates a more significant zone of sharpness, which is particularly useful in landscape photography or situations where one wants to ensure both the subject and background are in focus. For instance, if you were to photograph a landscape scene and used a small aperture like f/16 or f/22, you would achieve a greater depth of field, resulting in sharp details both close to the camera and far away. In contrast, a larger aperture (smaller f-stop number) would limit the depth of field, isolating the subject from the background by blurring it out. Thus, the correlation between aperture size and depth of field is a critical concept in photography, especially concerning composition and controlling focus. Therefore, as the lens opening decreases, depth of field invariably increases, allowing for greater creative control over which elements of the scene are in focus.