Certified Professional Photographer (CPP) Practice Exam

In photography, which f-stop value can improve focus by reducing chromatic aberration?

1. f/4

2. f/8

3. f/11

4. f/32

The correct answer is: f/32

The f-stop value that can improve focus by reducing chromatic aberration is the one that closes the aperture significantly, allowing for greater depth of field and better sharpness across the frame. Using a very small aperture, such as f/32, minimizes the light entering the lens, which can be beneficial in mitigating chromatic aberration. This optical phenomenon occurs when different wavelengths of light do not converge at the same point after passing through the lens, leading to color fringing around the edges of an image. By stopping down the lens to a small aperture like f/32, the light rays are forced to pass through the lens in more constrained paths, which helps to keep the wavelengths from separating as much. This results in a clearer image with more accurate color reproduction and improved focus throughout the photograph. In contrast, larger apertures (e.g., f/4 and f/8) may not control chromatic aberration as effectively because the light can enter the lens more freely, leading to a greater likelihood of color fringing. While f/11 may provide some benefits over wider apertures, it may not be as effective as the very small aperture of f/32 in minimizing these aberrations.