F-number

The F-number, or f-stop, is a measurement that describes how wide or narrow a camera lens's aperture is. A lower F-number (like f/2.8) means the lens opening is wider, allowing more light to hit the camera sensor, which is helpful in low-light conditions. A higher F-number (like f/16) indicates a narrower opening, letting in less light. F-number also influences the depth of field—the amount of the scene in focus—where lower numbers create a blurred background (shallow depth), and higher numbers keep more of the scene sharp (deep depth).