Aperture refers to the size of the opening that lets light through the lens into the camera’s sensor. One way picture aperture is to think of the iris of your eye. When you’re in a low light situation the iris of your eye will open all the way to allow the most amount of light in. When you’re outdoors in bright sunlight the iris of your I will close to limit the amount of light let in. The aperture of your lens is opened and closed with the use of aperture blades, these blades produce the same effect that the iris of your eye produces. Aperture can also be referred to as F stop, iris, and speed.