Aperture is one of the key topics that needs to be discussed when you are learning photography. In fact, as you likely already know there many books dedicated solely to explaining the topic of aperture. One of the best books that helped explain the topic of the aperture to me in much greater detail then I am going to get into, was Understanding Exposure by Bryan Peterson.  Aperture is one of the three variables that photographers can control when taking a picture.  The other two are Shutter speed and ISO.  Which are also covered in Bryan Perterson’s Understanding Exposure
What is aperture? if you want the technical explanation, the aperture is the size of the opening in a camera lens at the time a picture is being exposed.  Aperture is expressed in terms of ‘f-stop’ or ‘f/number’, such as f/4.5 or f/16.  Just to add to the confusion, the smaller the f-stop the larger the opening. The larger the aperture opening means that less of the scene will be in focus.  Which was completely counter-intuitive to me.  As well a large aperture lets more light into the camera, while a small aperture lets less light into the camera.  Confused yet?  I was until…

I was taking a Nature and Landscape Photography course at Georgian College, the instructors’ name was Bill Fell. Bill was the best instructor that I had, during my time at Georgian College. He believed that to learn photography you had to get out and photograph. During an outing, Bill was giving his in the field lesson and he said something that was very powerful. It was the simplest and I think the easiest to understand explanation of aperture that I have ever heard, and here it is. The bigger the number (f-stop) the more that is in focus, the smaller the number (f-stop) the less that is in focus. That’s it, that is how simple a very complex subject can be explained.

The bigger the number (f-stop) the more that is in focus, the smaller the number (f-stop) the less that is in focus

Let me show you an example…

The above photographs are the actual pictures that I took while experimenting with aperture when I was first learning photography.  As you can see the smaller the f/number has far less in focus than the larger f/number.

Ultimately, this is a very simplistic explanation of aperture.  Generally, this rule is true.  If you really want to get your head around the concepts of aperture, get out and shoot.

Aperture Exercise

  1. Find something that you can photography that has a decent amount of separation from objects in the background.
  2. Try and set your camera up to an equal distance from the subject, as the subject is from the background.
  3. Put your camera in aperture priority mode (“A” on Nikon cameras, or “Av” on Canon cameras).
  4. If you have a zoom lens, set it to the widest it will go.  If you have an 18mm-55mm lens set it to 18mm.
  5. Start at the smallest f/number usually around f/4.5, take a picture, then change the aperture to the f/number up.  Do this until you can’t go any higher usually around f/22.
  6. Compare the resulting images.  especially the first and last images that you took, see the differences?
  7. If you have a zoom lens repeat step 5 and 6 with your lens set to the longest setting.  If you have an 18mm-55mm zoom set it to 55mm.
  8. Compare the images from step 7 to the images you took in step 5.  Notice that at the longer the zoom setting (ie 55mm) with the same f/number less of the image is in focus.
  9. Repeat steps 5 and 6 keeping the camera settings the same but moving the camera closer to the subject.
  10. Now repeat steps 5 and 6 keeping the camera setting the same but moving the camera much further away from the subject.

You should notice that the images that you took in step 9 have less in focus than the images that you took in step 10.  If so you are well on your way to understanding how aperture affects the look of your images.

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