In photography, the aperture controls the amount of light passing through a camera lens. Most often, an iris diaphragm is used to control the opening. The various settings are called f-stops. The smaller the f-stop, the larger the opening. Standard f-stop values are f1.8, f2.8, f4, f5.6, f8, f11 and f16.
Figure A = f1.8
Figure B = f5.6
Figure C = f11
Aperture can also be used to control depth of field. Depth of field is a technique used to focus on a fixed point in a scene, called a focal plane. The area around the focal plane remains in focus, while the rest of the image is blurred. More blurring occurs when the aperture is wider (set to a smaller f-stop).
The next illustration shows the effect of depth of field in a scene. The focal plane is set short, so that the chair is in focus, leaving the background blurred.
