Which descriptor is used for the numbers that describe the size of the aperture opening?

• A. Shutter Speeds
• B. ISO Rates
• C. Focal Lengths
• D. F-Stops

Answer: (D)

Aperture size is described by f-stops. The numbers you see as f/2.8, f/4, f/8, and so on are called the f-number or f-stop. They express the ratio of the lens’s focal length to the diameter of the aperture. A smaller f-number means a larger opening and more light reaching the sensor; a larger f-number means a smaller opening and less light. This also affects depth of field, with lower f-stops giving more blur and higher f-stops giving more sharpness across the scene. The other options describe different camera controls: shutter speed is how long the sensor is exposed to light, ISO rates describe sensor sensitivity, and focal length determines magnification and field of view.