What is the correct relationship among aperture, f-stop, and lens speed?

• A. The larger the f-stop, the faster the lens
• B. The smaller the f-stop, the smaller the aperture
• C. The smaller the f-stop, the larger the aperture, and the faster the lens
• D. Aperture has no relation to f-stop

Answer: (C)

Understanding how aperture, f-stop, and lens speed relate is essential: the f-stop is the setting that describes the size of the lens opening, with a smaller f-number meaning a larger aperture. A larger opening lets in more light, so you can use a shorter shutter or a lower ISO to achieve the same exposure, which people call a faster lens. Conversely, a larger f-number yields a smaller opening, less light, and a slower lens. So the statement that a smaller f-stop corresponds to a larger aperture and a faster lens captures the correct relationship.