ABSTRACT
Inside the lens there’s an opening called the aperture. This opening controls how fast the light comes into the lens. You can have a very large hole or a tiny one. A big hole is going to let a lot of light into the lens very quickly. With a small hole the light comes in much slower. Every lens allows you to change the size of the opening by changing the aperture setting. Take a look at these photos to see the actual size of the openings and the number that goes with each one.
