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Photography 101: Aperture

What is Aperture? How does it affect photos? And how do I set my f-stop properly?

We briefly covered aperture in our Beginner Guide, which if you haven’t checked out yet… (you should). Here, we’ll deep dive into the meaning of one of these tools as a photographer.

Let’s look at the meaning of the aperture. Oxford Dictionary defines it as “a small opening, hole, or gap.”

By logical extension then, we can apply this definition to photography. Aperture in the photography world is the opening in the lens through which light passes through.

To achieve this, camera lens manufacturers fit their lenses with a set of blades. The positioning of each blade relative to the next is determined by the f-stop setting you choose for your photo. The smaller the f-stop value, the larger the opening. And vice-versa, the higher the f-stop value, the smaller the opening.

But let’s stop for a second and get a visual sense of what we just defined.

Infographic about aperture: 
- aperture controls the amount of light through the lens
- blades create an octagonal opening
- f-stop controls the positioning of the blades, thus the opening size
- additionally controls the depth of field

How Does Aperture Affect My Photos?

So now that we know what aperture is, let’s look at how it affects the photos that we take. Specifically, there are two areas that are controlled by aperture: amount of light (exposure) and depth of field.

Exposure Control

Here are two scenarios for you to consider:

  1. You take a photo and the image is very dark (underexposed).
  2. You take a photo and the image is very bright (overexposed).

In the first case, this means that there is not enough light passing through the lens. Based on our definition above, that means that the opening is too small, or your f-stop value is too high. To improve this image, you would maybe consider using a lower f-stop value.

Credit: Dawid Skalec

In the above second scenario, the photo is too bright. Too much light is passing through the lens and overexposing the image sensor. Your f-stop value is too low. Try raising the value of your f-stop and taking the image again.

Depth of Field

Depth of field controls how much of the composition in front of and behind the subject of your image is in focus.

The easiest way to describe this in practicality is with an experiment. If you close one eye and make a slightly closed fist “lens” (imagine you’re looking through a make believe telescope), this same effect is made. Close your fist more, decreasing the size of the opening, and your focus get sharper around the specific subject you’re looking at.

Our camera technology is a mechanical representation of our eye’s natural ability to regulate light. This experiment can have a stronger effect if you are someone who wears glasses. You’ll notice a word or object far away that is out of focus to you normally, you’ll have an easier time seeing it through your make shift telescope.

How does this relate to the f-stop value? Unlike the inverse relationship between the value and the amount of light passing through that we’ve described above, depth of field is a direct relationship.

This means that a smaller f-stop value will have a more defined depth of field. The composition in front of and behind your subject will be out of focus.

A higher f-stop value will have a broader depth of field. More of your image will be in focus. For landscape or nature photography, it’s often recommended to use this higher f-stop to ensure a sharper image overall.

Summary

Aperture is often one of the most difficult things to understand in beginner level photography because of the multiple affects it has on an image. The inverse and direct relationships to exposure and depth of field make it even more challenging to remember. But we’re going to make this as simple as possible with the graphic below:

Info guide on common aperture settings and how they affecting lighting and depth of field.

Now, you’re an f-stop pro! Take a step back and breathe a sigh of relief.

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