The three pillars: Aperture

1.) We would closely relate Aperture to the pupil.

2.) The smaller the Aperture the larger the f-stop. The higher the Aperture the smaller the f-stop.

3.) The larger the Aperture the smaller the focus of the field meaning that the focus of your picture will be small and sharp while everything else is blurred. The smaller the Aperture the larger the focus meaning deeper depth of field.

Aperture f 2.8

Aperture f16 (comparison to f 1.4)