How Aperture Works on Your Camera — Simply Explained

This article is a lesson in our online photography course.

In the photography course, in addition to this written section, you’ll also find a video where we explain how aperture works. However, that video is reserved exclusively for our course participants.

Aperture is one of the most important settings on your camera.

Once you understand and master aperture, photography becomes a whole lot more fun. So, let’s dive right in.

In this lesson you’ll learn, among other things:

• How to make the background of your subject appear blurry.
• How aperture is connected to shutter speed.
• How to set the aperture and use it for your photos.

We’ll start by defining aperture for you and explaining its function as simply as possible. Don’t be discouraged if you don’t understand everything right away.

With each sentence, things will become a little clearer — and after you’ve tried it out in practice, hopefully no questions will remain. So go ahead and grab your camera.

One small note before we get started:

There are two fundamental settings you can use to influence the exposure of your photo. One of them is the aperture, which we cover in this lesson.

The second is the shutter speed — that is, how long your image is exposed. The longer the shutter speed, the more light hits the sensor. We’ll cover shutter speed in more detail in the next lesson. For now, it’s enough to know that shutter speed exists.

Aperture: A Quick Definition

The aperture is the rear opening of your lens. You control how large this opening is, and that determines how much light hits the camera’s sensor.

The size of the opening is indicated by the f-number. When a photographer talks about the f-number they used for a particular photo, they use values like f/1.8, f/2.8, or f/5.6.

Here’s the interesting part: the higher the number after the f/, the smaller the aperture opening. And conversely — the lower the f-number, the larger the aperture opening.

Take a look at the image below. You can see it really clearly there.

So when you set f/2.8, a relatively large amount of light hits your sensor — and when you set f/13, only very little light gets through.

We’ll explain what that’s useful for shortly and try it out in practice too. You’ll also see the differences in photos taken at different f-numbers.

But first, we need to work through a bit of theory. Don’t give up — it’ll all make sense in a moment. So, back to the f-number.

Burn this rule into your brain: the smaller the number after f/, the more light hits the sensor:

Small number, large opening, lots of light — large number, small opening, little light!

If that still sounds illogical, just think of the numbers after the f as fractions. Is 1/16 (one-sixteenth) larger than 1/8? No — exactly. Just because 16 is a bigger number doesn’t mean 1/16 is more than 1/8. So: f/16 is smaller than f/8, and therefore lets in less light.

Say it out loud one more time: small number, lots of light — large number, little light!

Ok, take a quick breath. Let’s keep going.

Here is a typical aperture series — from left to right, the aperture opening gets smaller:

Which numbers you can set depends on your camera and, above all, on your lens. So it’s perfectly normal if your camera starts at a different f-number or if you have f-numbers in between the ones shown here.

Many entry-level lenses, for example, don’t offer small f-numbers like f/1.4, f/2.0, or f/2.8. They start at f/3.5.

How to Set the Aperture on Your Camera

Enough theory — now let’s try aperture out in practice. Have your camera handy for this.

Mode A

Every camera has various modes. The modes M, A, S, and P are typically always included. On some cameras, they’re called M, Av, Tv, and P. To try out aperture in practice, set your camera to mode A or Av. The A stands for Aperture.

In mode A, you manually set your f-number — in other words, you decide how much light you let onto the sensor.

The camera then automatically selects the shutter speed that matches your chosen f-number, so your photo is always properly exposed.

Mode A is also often called aperture priority or shutter speed automatic. Just pick whichever name you prefer, or simply call it mode A.

If you’re just starting out, you might be wondering what shutter speed has to do with any of this. Don’t worry about that for now.

In mode A, the camera handles it automatically. For now, we’re focusing solely on the f-number and mode A. We’ll take a closer look at shutter speed in the next lesson.

Once you’ve set your camera to mode A, your next step is to dial in the f-number you want to use.

On many cameras, you control the f-number with a small dial on the front right. If you can’t immediately find where to change the aperture on your camera, just check your manual.

To see which f-number you’ve set, look through the viewfinder or check your display — depending on your camera type. You’ll find the f-number with the f/ at the beginning.

How to Use Aperture in Your Photos

Now let’s look at how you can actually use aperture to your advantage.

#1 Shooting in Low Light Conditions

The aperture opening determines how much light hits your sensor. As a reminder: large opening, lots of light — small opening, little light.

In low light conditions, you can open your aperture wide and still let enough light onto the sensor to get a properly exposed photo.

In the upcoming lessons, we’ll cover shutter speed, manual exposure, and ISO. Once you know all these photography terms and understand how they relate to each other, a lot will click into place.

For now, it’s enough to know that a wide aperture opening can help you shoot in low light.

The photo below, for example, was taken in very low light. It was already dark outside and the scene was only lit by lanterns that weren’t giving off much light at all. We opened the aperture wide to still be able to get a decent shot.

#2 Depth of Field and Blurry Backgrounds

But aperture isn’t just about controlling how much light enters your camera. Changing the aperture also gives you a really important creative tool: depth of field. With your choice of f-number, you decide whether the background of your main subject is tack sharp or beautifully blurred.

You’ve surely seen photos where a person appears sharp but the background is soft and out of focus. That’s exactly the effect you can achieve by adjusting your aperture.

We’ve picked out a couple of our own photos to show you. You can see that the focus is on the face while the background is out of focus.

The first photo of Jenny was taken at f/5. That’s not an extremely wide aperture at all, yet you can already see how noticeably the background has gone soft.

In the second photo the effect is even more pronounced. It was taken at f/1.8. Here, only the incense stick in the foreground is sharp — the background is barely recognizable.

You can also achieve the opposite effect. By closing the aperture down a lot — choosing a large f-number — you get a very high depth of field. Instead of a blurry background, everything in your photo will be sharp.

The photo below was taken at f/11. Both Basti in the foreground and the city in the background are sharp.

Through these example photos you’ve already gotten a first impression of how aperture affects depth of field.

Now let’s look at this again with a practical example. We’ve drawn a little something for you.

The first image shows the starting situation: you’re standing at the end of a soccer field and want to photograph a soccer player. To keep things interesting even for non-soccer fans, we’ll pick a particularly photogenic player: Mats Hummels.

So there you are, standing on the sideline with your camera at the ready, focusing on Mats Hummels.

That’s what the first image shows. The teal line represents your focal plane.

A photo of Mats Hummels at an aperture of f/2.8

Your camera is set to mode A and you’ve set the aperture to f/2.8 (wide open, lots of light). Mats Hummels and everything within the gray-shaded area is sharp. The rest of the soccer field is blurry.

So we’ve achieved exactly the effect from our first example photo above. Mats Hummels’ face is in focus, the background is blurry. The goalkeeper in the opposing goal would only be vaguely recognizable.

Our starting situation: We want to take a great photo of Mats Hummels

Now we want to also get the goalkeeper in the right goal — let’s say Manuel Neuer — sharp in the photo.

So you increase the f-number to f/8 (the aperture closes, less light comes in). The area behind Mats Hummels gets a bit sharper, but we still can’t see Manuel Neuer clearly (image 3).

A photo of Mats Hummels at an aperture of f/8.0

Not enough. Let’s go to the extreme and increase the f-number to f/22 (the aperture is almost closed and very little light gets through).

As you can see in the image below, we’ve now brought not only Mats Hummels and Manuel Neuer into sharp focus, but the entire soccer field.

A photo of Mats Hummels at an aperture of f/22

As you can see, the f-number doesn’t only affect the background. The area in front of your focused subject also becomes sharper or softer when you change the aperture.

Note: We only used the f/22 example for illustration. In practice, we shoot at a maximum aperture of f/13. At higher f-numbers, many lenses actually start to lose sharpness for technical reasons — so don’t push that value too high.

After that somewhat abstract example, here are real photos showing the relationship between aperture, depth of field, and focal plane:

You can actually replicate this effect with your own eye. Hold your hand about eight inches in front of your face and focus your gaze on your fingers. Your fingers are sharp and the background is blurry, right?

Now focus on an object in the background. Your hand goes blurry and the background goes sharp. It always depends on what you’re focusing on — and it works exactly the same way with your camera.

This article on aperture photography is a free sample lesson from our 22places Online Photography Course. We explain the complete fundamentals of photography in easy-to-understand texts and videos — and you’ll soon be taking breathtaking photos yourself! Click here for more info: Online Photography Course.

In the photography course, in addition to this written section, you’ll also find a video where we explain how aperture works. However, that video is reserved exclusively for our course participants.

Which Aperture Should You Use?

Now the question naturally arises: which aperture should you use in which situation? Honestly, it’s a matter of personal preference. Still, here’s a quick guide to which aperture values make sense for different scenarios.

A shallow depth of field is recommended when you want to draw the viewer’s attention to your main subject by blurring the background — portrait photography is the classic example. You achieve this with small f-numbers between f/1.8 and f/4. There are even lenses that go down to f/1.4 and lower — but those tend to be quite expensive.

If you want to photograph a group of people rather than just one person, you’ll need a larger f-number — close the aperture down a bit. It would be a shame if only the people in the front row were sharp and everyone behind them was blurry.

Closing the aperture brings more depth of field into the image and ensures everyone in the photo is sharp.

A lot of depth of field is also ideal for landscape photos, so the scene looks as true to life as possible. When you look at a landscape with your own eyes, the foreground, midground, and background are all sharp (unless you left your glasses at home).

For landscapes, we’d recommend shooting with a closed-down aperture — f-numbers like f/11 or f/13.

But as we said, it’s also a matter of taste. Imagine you’re walking through the Sahara and suddenly spot a beautiful red rose. Pretty unlikely, but who knows.

The Sahara sand isn’t particularly interesting to you, so you want to focus only on the rose. You open the aperture wide (e.g., f/2.8) and focus only on the flower. The rose is sharp, the sand is beautifully blurred.

But now imagine the sand is so dry it has formed beautiful cracks, with this gorgeous red rose blooming right in the middle of them. In that case, the sand would add something to the photo — so you’d want both the rose and the background sharp, and you’d shoot with a closed-down aperture (e.g., f/11).

But be careful: You might be tempted to close your aperture down as far as possible to get maximum sharpness throughout. Unfortunately, that generally doesn’t work. While depth of field does increase as you close the aperture, overall image sharpness starts to decrease again beyond a certain f-number.

At which f-number this happens varies from lens to lens — every lens has a specific aperture value at which it achieves the greatest overall sharpness. That’s usually somewhere between f/7.1 and f/11.

Our tip: Avoid very large f-numbers to avoid blurry photos. Starting at f/16, things get critical with many lenses. An aperture of f/22 often noticeably reduces sharpness across the entire image.

Exceptions always prove the rule. If you have some time, put your camera on a tripod and take several photos of the same subject at different aperture settings.

Afterward, compare the images and you’ll be able to see exactly at which aperture your lens is sharpest — and at which f-number things start going soft. That way you’ll know exactly how far you can push your lens.

A quick summary
Open aperture → e.g., f/1.8 or f/3.5 → Shallow depth of field → e.g., for portraits and any situation where you want to focus on your main subject with a blurry background.

Closed aperture → e.g., f/11 or f/13 → High depth of field → e.g., for landscape or architecture photography, and any situation where you want the image sharp from foreground to background.

Extra Knowledge: Full Control Over Depth of Field

Aperture is actually just one of three factors that influence depth of field in your image. This will become clearer in the upcoming lessons, but for the sake of completeness we’d like to mention it here.

So let’s take a brief detour into depth of field. If you’d prefer to focus on aperture for now, feel free to skip this section and come back to it later.

Here are all the factors that influence depth of field:

• The aperture
• The focal length of your lens (wide-angle vs. telephoto)
• The distance between your camera and your subject

Here’s a handy overview of how each factor affects depth of field:

We’ve already covered aperture and depth of field. Now let’s look at the other two factors.

Key Point: Focal Length

We’ll cover focal length in one of the next lessons. For now, here’s a really brief explanation: focal length corresponds to the zoom of your camera — short focal length = less zoom = wide-angle, long focal length = more zoom = telephoto.

When you shoot with a wide-angle lens, you’ll still have a relatively large depth of field even with the aperture wide open. The photo of Basti below was taken at a relatively wide-open aperture of f/4.

However, since it was shot at a short focal length of 18 mm and the distance to the subject was relatively large (see next point), the photo still has a high depth of field.

With a telephoto lens, it’s the other way around. Even if you shoot with a fairly closed aperture, you’ll still have a relatively shallow depth of field.

You can see this clearly in the next photo. Even though it was taken at a relatively closed aperture of f/8, the background is blurry — because it was shot at a very long focal length of 300 mm.

Key Point: Distance Between Subject and Lens

If you’re taking a portrait and your subject is standing half a meter away from you, the background will be very blurry. If you take a big step back and shoot again with the same settings, the depth of field won’t be quite as shallow anymore.

As you can see, aperture isn’t the only factor responsible for depth of field.

Practice Assignments

Alright. Now let’s try all of this out. Grab your camera — you’re going to need it.

Here’s what you need for the first practice attempts:

• Your camera
• Your camera’s manual, in case you’re not sure how to change the f-number
• A subject — maybe a small stuffed animal or something similar that can serve as a model

You can do the first exercises easily at home.

Make sure you have plenty of light available. It’s best to turn on every lamp you have. This applies to indoor shots too.

Once you’ve turned on your camera, set the dial to aperture priority — mode A (or Av on some cameras). When you look through the viewfinder or at your display, you’ll see several numbers along the bottom. One of them should have an f in front of it. Found it? That’s your f-number.

This is roughly how the f-number will appear in your viewfinder or on your display:

Your viewfinder should look something like this. The value with the letter F in front of it is the f-number.

Now look through the viewfinder and focus on your subject. To set the f-number, briefly press the shutter button first to focus, then change the f-number using the dial.

#1 Get Familiar with Setting the Aperture on Your Camera

Setting the f-number varies a little depending on which camera you have — trying things out usually works best. Often there’s a small dial on the front right of the camera that lets you change the f-number.

If that dial isn’t there, experiment to find out which dial changes the f-number, or check your manual. Found it? Great — you’ve already completed the first task!

#2 Discover the Effect of the Aperture Setting

Alright, now let’s take some photos. Pick a subject and photograph it at various f-numbers.

Try out the full range of aperture settings — including very wide-open and very closed-down. Do you see how your subject and the background change?

When you select very large f-numbers, you’ll probably need to put your camera on a tripod or rest it on a table. Since very little light hits the sensor through such a small opening, your camera compensates with a longer shutter speed, which can cause camera shake. You’ll learn more about shutter speed in the next lesson.

#3 Play with Depth of Field

Once you’re comfortable setting the aperture, try intentionally using shallow depth of field in your shots. Choose the widest aperture your lens allows (smallest f-number) and look for subjects that look great with a blurry background.

Also try photographing the subject from different distances and see how that affects the background blur.

Got the hang of aperture? Awesome — that’s already a huge step on the road to learning photography. In the next lesson, we’ll tackle shutter speed, the second really important setting on your camera.