Certified Professional Photographer (CPP) Practice Exam

How does increasing the focal length of the lens affect the depth of field?

1. It makes it deeper

2. It makes it more variable

3. It makes it shallower

4. It has no effect

The correct answer is: It makes it shallower

Increasing the focal length of a lens results in a shallower depth of field. This means that when using longer focal lengths, the range of acceptable focus is reduced. As a consequence, objects that fall outside this narrower zone appear out of focus more quickly than they would with a lens that has a shorter focal length. This effect occurs because longer focal lengths compress the perspective, which not only narrows the area that appears sharp but also tends to isolate the subject from the background and foreground. This characteristic is especially desirable in portrait photography, where isolating the subject through a shallow depth of field enhances visual focus and aesthetic appeal. Understanding how focal length interacts with depth of field is crucial for photographers, as it enables them to control the visual narrative of their images, guiding the viewer's attention and creating more compelling compositions.