Professional photographers rely on aperture to control the amount of light that passes through the camera’s image sensor. The term refers to the iris in the camera lens, which opens or closes to allow in different levels of light. A camera’s aperture is measured in f-stops.

Aperture control performs two essential functions on a DSLR camera. In addition to managing the amount of light that passes through the lens, resulting in brighter or darker images, it also controls depth of field, which is a technical term for how sharp or blurry objects appear outside of the object at the center of the camera's focus.

F-stops go through a huge range, especially on DSLR lenses. However, your minimum and maximum f-stop numbers depend on the quality of your lens. Image quality can suffer when you set a small aperture, so manufacturers limit the minimum aperture of some lenses.

Most lenses have an f-stop range of at least f3.5 through f22, but the f-stop range of different lenses can vary from f1.2 through f45.