Thursday, November 3, 2011

Aperture, F/stop and Depth of Field Explained!

Every profession has its own lingo. It is the same with photography.  Photographers say things like,
“Use a wider aperture,” or, “What f-stop are you using?”  So, What is an f-stop? What is Aperture?

For those who want to learn more about topics like aperture, online universities have
photography courses.

 Aperture is a term for a measurable expression of how much light is entering a camera lens. F/stop is a number assigned to a specific Aperture.

All cameras have a lens which light passes through to help record the image. However, to get a proper
 exposure so you do not have underexposure or overexposure, light must come in through the lens in the
 correct amount needed.  The f-stop(aperture) on a camera helps control the exposure.

The “F” in f-stop stands for focal length.  The focal length divided by the diameter of the pupil ,
or the amount of light entering the lens is how the f-stop is determined. The numbers f/2 or f/16 are
 expressions of  f-stops.   The number denotes how wide  the opening in the aperture is.  The aperture
 is an opening behind the camera lens. The aperture works like the pupil of the eye. It gets wider when
there is not a lot of light and smaller when there is more light. Test this out. Get a flashlight and go
to a mirror. First look into the mirror at the black part or pupil of your eye. Notice the size. Now turn
on the flashligtht and point it at your eye.  While looking in the mirror you will notice that your pupil
gets smaller. This is exactly how an apeture works.  The more light, the smaller the pupil of your eye, the
less light the wider the pupil of your eye.  Now here is the weird part. When you apeture is open wider, the
f-stop will be a small number like f/5.6 or f/2(if you have a fast lens).  If the apeture is smaller, you will
 have a number like f/16 or f/22. The Aperture also controls the Depth of Field in your photo. To put it simply, Depth of field controls what is in focus in your photo. If you use a wide Aperture like F/1.4 you will have shallow Depth of field, or what is in focus will be shallow.  Here is an example of what shallow Depth of field looks like.

This photo was taken at F/1.4

If you use a small Aperture like f/22, you will have a photo where the depth of field is not so shallow. Below is an example.

This photo was taken at F/22

There are other things that control depth of field like the length of your lens and the distance you are from your
subject but that is another lesson. Anyhow, You should get the general point of this lesson.  If you have questions or need more help understanding, leave a comment below and I will do my best to answer it. Thanks! Hope you enjoyed this short lesson!!


  1. Great information for me as a beginner. Glad I found you on Twitter.

    Question: If a wide aperture gives "shallow" depth of field, what term do you use for focus on a small aperture? Would that be "deeper" depth of field?


  2. Dan, that is probably the best question I have ever had on this blog. It is usually called Deep Focus or maximum depth of field. If you have any more questions let me know. Thanks Dan!

  3. I am a beginner in photography. I have always liked photography, but just here lately been really interested in learning more. I have actually been working with a photographer to learn more. Im loving it. I dont plan on actually doing any photography classes. I been learning alot online. Your mini lessons are great. Probablly one of my favorites you explain things so well. I'm super excited to go out and try what I have learned. Hope everything turns out okay. Wish me luck!