Inside each lens is a diaphragm that can open and close, the size of the opening at any given setting is what we refer to as the aperture setting. On our cameras we refer to specific size settings as f-stops such as f/2.8, f/5.6, f/11, etc. While the obvious value of adjusting the aperture is to control how much light enters the camera, there is a secret hidden world beneath the hood that we will need to get a grasp of as well, but let’s start at the basics first.
For a given ISO setting and shutter speed we can adjust the amount of light entering the camera by adjusting the aperture, a smaller diameter (higher f-stop value) will allow less light in, while a larger aperture (smaller f-stop number) will allow more light it. If we refer to the Sunny 16 rule, we know that on a bright sunny day, if we are using ISO 200 and a shutter speed of 1/200th then we will get a good exposure at f/16. As the sun goes down and there is less light, we need to allow more light into the camera, we can do this by opening the aperture up (again, using a smaller number) to allow more light in. This sounds easy enough right?
