What Is An F Stop?

An f stop is a term used in photography and denotes the size, expressed as a ratio, of the aperture in a camera that regulates the amount of light falling on the lens.

The amount of light falling on the lens is proportional to the size of the aperture and an f spot expressed as f / 2 will let in more light as compared to an f spot expressed as f / 8.

The main function of the f spot is that it affects the depth in the picture and a picture of say a flower taken where the f spot is f / 2 will highlight the flower while the background will be less prominent. On the other hand a picture taken with an f spot of f / 8 will make the picture appear with the flower and background in visible degree.

The ratio can be expressed as y = f / x where f is the focal length of the lens and x is the diameter of the aperture and y is the focal number expressed as f / y (f spot). Thus if the f spot is expressed as f / 2 it means the diameter of the aperture is one half the focal length.