What is Aperture?

What is Aperture?

What is Aperture?

Webster’s dictionary tells us this:

ap·er·ture

 noun
\ˈap-ə(r)-ˌchu̇r, -chər, -ˌtyu̇r, -ˌtu̇r\

Definition of APERTURE

1: an opening or open space 

2 a : the opening in a photographic lens that admits the light

b : the diameter of the stop in an optical system that determines the diameter of the bundle of rays traversing the instrument
c : the diameter of the objective lens or mirror of a telescope

Like the definition above, Aperture refers to the size of the opening in your camera lens that determines the amount of light falling onto the film of your camera or, in a digital camera, the amount of light falling onto the image sensor. The diameter or size of that opening  is controlled by a diaphragm which is similar to the pupils of our eyes.  Aperture size is measured in f-numbers or f-stops. (These are the little numbers on on the lens barrel – f22 (f/22), f16 (f/16), f/11, f/8.0, f/5.6 and so on)  Moving from one f/stop to another doubles or halves the amount of light reaching your film/sensor.

What really confuses people is that the larger the f/stop number, the smaller the diameter of the opening. So an f/stop of f/22 will give you a smaller opening, therefore a smaller amount of light than an f/stop of f/1.8. So the smaller the f/stop number, the LARGER the opening.

What does this all mean to those of  you who have no idea how aperture applies to you? I know you’ve seen those photos where the foreground or the subject is completely in focus and the background is blurry or fuzzy. That’s called Depth of Field and it’s achieved by adjusting your aperture settings.

Depth of  Field is just the amount of  your photo that will be in focus. A large depth of field (or DOF) means that most of your photo will be in focus no matter how close or far away you are. You achieve this effect with your larger number f/stop settings like f22.

A shallow DOF (or small) means that only part of your image will be in focus while the rest will be fuzzy, like the photo I described earlier. You achieve this by using the smaller number f/stop setting such f1.8.

The best way to figure out what your camera settings will do is to just go out and experiment for yourself with your own camera. Take a series of photos with different  settings and see for yourself.