When setting up an image, the aperture and lens you choose makes a big difference.

It’s important to know when to isolate your subject by shooting with a large aperture like f/2 or when to stop down to capture more of the scene with a small aperture like f/16.

Experimenting in aperture priority mode can help you visualize how changing the aperture affects both your subject(s) and your background. These exercises will help you understand how your area of focus changes as your aperture changes and also how using a different lens drastically changes the affect.

Exercise 1: area of focus

What you need:

  1. a camera
  2. a lens
  3. multiple subjects (stuffed animals and other inanimate objects work great)

What to do:

  1. Set your camera to aperture priority mode (Av for Canon).
  2. Set your ISO. The less light you have available, the higher you should start.  My ISO varies between 1600 and 4000 in the images shown. As you stop down (the aperture number increases) you will need to increase your ISO.
  3. Open up your lens as wide as it goes by setting your aperture to the lowest number possible.
  4. Set up your subjects so they are staggered. There should be several inches between the front and the back of all your subjects.
  5. Focus on the object in front and keep your focus the same for the whole series. Gradually increase your aperture to f/5.6 then f/10 then f/22.

When you compare the images, try to look for the areas of focus in each image. This slice is very narrow when you’re wide open and then the area expands as more and more becomes in focus. In these examples, I went from f/2 to f/20.

35mm photo at different apertures by Alicia Gould

If you have time, keep your set up the same but use a different lens. You’ll notice I’m much further back to capture the same set up when I change to my 135 mm lens. When I’m further away, it doesn’t take as long for all the objects to be in focus.

135mm photos at different apertures by Alicia Gould

Exercise 2: focal length

What you need:

  1. a camera
  2. 2 prime lenses or 1 zoom
  3. a subject
  4. background items

What to do:

  1. Set up larger items in the background.
  2. Set up your subject a few feet away from the background.
  3. Using the first lens (or zoom at the widest mm possible), fill the frame with your subject and shoot using two or three different apertures (f/2.8, f/8, and f/22 are good suggestions to see the full difference).
  4. With the same lens, now back up and capture your subject’s ‘full body’. Use the same apertures you chose previously.
  5. Now switch your lens (or adjust your zoom to the longest mm possible) and repeat: fill the frame and change your aperture; then move back.

close up photos at different apertures from Alicia Gould

full body photo at different apertures by Alicia Gould

In the pullback, you can see that the set up didn’t move at all, only I did! The lens I used not only changed the area of focus, but the look of the background. With a shorter focal length (35mm) my background is much more in focus than at 135 at the same aperture.

Photographers love lenses that open up wide to isolate their subjects when capturing portraits. They want that smooth bokeh that comes with using apertures of f/1.2 to f/2.8. The last exercise demonstrates that your distance from your subject also plays a big part in the background, it’s not just about the aperture. Try coming up with your own exercises by adjusting your aperture, lens and distance! If you’re a visual person like myself, it’s fun to ‘see’ the changes.