Understanding Aperture

Aperture. It’s a hole.


The larger the hole, the more light comes into your lens.

The smaller the hole, the less light comes into your lens.

Let’s try a little experiment to see what else aperture does.

  • Look at something, preferably nonmoving or changing.
  • Open your eyes REALLY wide.
  • What did you notice?
  • Now, squint your eyes as you look at the same thing.
  • What do you notice now?

If your eyes are similar to mine, when open widest it was difficult to focus on any one part of your subject. But, when you squinted you were able to see much more detail.

The aperture of your camera works in the same way.

Wide aperture (big hole). Less in focus.

Narrow aperture (small hole). More in focus.

So what’s with that funky f/ number confusing you with its backward numbers then?

Ready for this? You might want to grab your second grader to explain this one.

It’s a fraction?


So guess what the F stands for? Fractional. Yep, fractional stops or f stop. You’ve heard it and now you can feel a bit more informed.

The f-number is part of an equation representing the focal length of the lens divided by the diameter of the lens’ hole.

The result is the f number.

Do you need to remember that? Probably not. But at least you can be a little less confused about what all the f talk is.

In practical terms, there are a few things to know about aperture.

A small f/# = a big hole = less in focus = more light into the camera

A large f/# = a small hole = more in focus = less light into the camera

So what can you do with all of this?

Small f/# | Wide Aperture

How do I blur the background is one of the questions I’m asked most! You can get a blurred background with a large aperture (small number). Blurring the background is useful when your scene is cluttered and you don’t want the viewer to see your dirty laundry! It can also help isolate a single item to draw attention to it.

To blur background work with three things:

  1. Wide aperture – the smaller the number the shallower your depth of field. Be careful when shooting “wide open,” it is very easy to miss your focus point!
  2. Distance between the subject and the background – the more space you leave between your subject and the background the more blur you can achieve.
  3. Longer focal length – use a longer focal length to get more blur in your background.

Large  f/# | Narrow Aperture

Landscape photography uses a narrow  aperture to get more of a scene appear in focus. It can provide sweeping beautiful views.

When shooting with a small aperture (large number) focus 1/3 into your photo so you have a foreground, middle, and background to the picture. It will be more pleasing and more interesting to the viewer. Try shooting at f/16 or f/22. Remember you will need plenty of light to get a shutter speed to stop motion and avoid camera shake.

Large depth of field works well when shooting multiple people or when the scene itself has appealing features. Large open fields, green areas, flowered areas, snowy scenes all lend themselves to a larger depth of field.

Let’s have a little fun! In this exercise, notice how adjusting your aperture changes the look of your image.

  1. Find two cooperative objects that you can easily move.
  2. Place your camera on AV or A mode.
  3. Place the objects in good, even light next to each other so that they almost touch.
  4. Set your aperture to f/4.0 or f/2.8 if available on your lens.
  5. Facing the objects, focus on the right hand object.
  6. Shoot.
  7. Stay in the same place, adjust your aperture to f/5.6.
  8. Shoot, focusing on the same spot.
  9. Adjust your aperture to f/8.
  10. Shoot, focusing on the same spot.
  11. Repeat, stopping down one stop more to f/11.
  12. Keep on playing if you’d like. Adjust to f/16 and then f/22.
  13. What do you notice?

Whether you go wide or narrow or somewhere in between, play with aperture to see the creative results you can achieve!