Aperture

Aperture controls the brightness of the image that passes through the lens and falls on the image sensor. It is expressed as an f-number such as f/2, f/8 etc. Lower the f-number, the larger the aperture and more light that passes through the lens. For example, changing the aperture from f/4 to f/5.6 halves the amount of light passing through the lens and halves the brightness of the image that falls on the image sensor.