Aperture

1. The aperture is most similar to the pupil of the human eye.

2. The smaller the Aperture the less light enters, the higher the Aperture the more light enters.

3. The Depth of Field is effected by the size of the aperture. By having a larger f-number the background objects will be more focused, and when having a smaller f-number the background objects will be more blurry. 

F2.8

F16