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How to Understand Aperture in Photography

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Aperture is one of the three elements that build up the exposure besides the shutter speed and the ISO. Getting to grips with taking an evenly exposed photo is a lot easier when you understand the aperture.

As you develop your photography skills, you will want to have more control over your camera. You will leave behind auto modes and start shooting in manual modes like aperture and shutter priority. You can bring out the best of your photography by controlling all three settings of the exposure triangle manually.

In a lot of cases, the aperture has the biggest impact on a photo. Using different apertures also opens up more creative avenues through unique effects. This article will teach you what they are and how to use aperture to your advantage.

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What Is Aperture?

The easiest definition for aperture is to say that it’s the opening of your lens. This adjustable “hole” in your lens is also called the diaphragm. If you take a closer look at your camera’s lens, you should see something like this:

Close up image of the aperture opening in a lens

The best way to understand the aperture definition is to think of it as the pupil of an eye. In low light conditions, the pupil is wider letting in as much light as possible. When there’s too much light, like direct sunlight, it shrinks to compensate for the amount of light. In photography, the lens of your camera works just like this.

Let’s follow this analogy. Would you use a wide or narrow aperture to photograph a darker scene like a beach after sunset?

You should already know the answer to this question. But if not, I’ll give you a little hint: If you enter any dark place, your pupil widens up.

As the diameter of the aperture size changes, it allows more or less light onto the sensor. This depends on the situation and the scene being photographed.

So, a smaller aperture (like f/11) allows less and a larger aperture (like f/1.8) allows more light in.

How to Understand the Aperture Values

Aperture can be confusing sometimes. Some people will say a wide or narrow aperture, but others might say a large aperture number or a small one. What is the difference? A wide aperture refers to the wide opening in the lens, where an aperture like f/1.2 or f/1.8 is being discussed.

Don’t worry if you don’t understand what these f/numbers are yet. This will be tackled in the next section, just follow along.

A larger aperture number refers to the number of f/stop when f/22 or f/32 is being discussed. A large aperture number, a narrow or a small aperture are the same things. One talks about the size of the number and the other relates to the size of the opening in your lens.

old film camera closeup

How Is Aperture Measured and Changed?

In photography, the aperture size is measured using something called the f-stop scale. On your digital camera, you’ll see ‘f/’ followed by a number. This f-number denotes how wide or narrow the aperture is. The size of the aperture affects the exposure and depth of field (also tackled below) of the final image.

Getting Familiar With the F-Stop Scale

What may seem confusing is that the lower the number, the wider the aperture. This means that your camera aperture settings will be wide open at a smaller f -stop number, like f/1.4 (usually this is the maximum aperture of a lens). At higher numbers, like f/16 or f/22, you’ll get a narrow, small aperture.

Why a low number for a high aperture? The answer is simple and mathematical, but first, you need to know the f-stop scale.

The scale is as follows: f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.


The most important thing to know about these numbers is the following. As the numbers rise, the aperture of the lens decreases to half its size with every stop. Half meaning that it allows 50% less light through the lens.

So if take an f-stop like f/2.8 and change it to f/5.6 our image will have four times less light than at the starting aperture size of f/2.8. This is because we skipped a whole stop (f/4) and stepped two stops up. Remember, one stop means 50% less or more light depending on widening up or narrowing down your aperture.

This is because the numbers come from an equation used to work out the size of the aperture from the focal length. You’ll notice on modern-day cameras that there are aperture settings in-between those listed above.

These are called third or 1/3 stops, so between f/2.8 and f/4 for example, you’ll also see f/3.2 and f/3.5. These are just here to increase the control that you have over your settings.

Now things begin to get a little harder. If you get confused, skip to the next section as the most important part has been covered.

For example, say you have a 50mm lens with the aperture set to an f-stop like f/2. How do you find out the width of the aperture? You need to divide the focal length (50mm) by the aperture (f/2), giving you a diameter of 25mm.

Then take the radius, multiply it by itself (radius squared) and multiply that by pi. The whole equation looks something like this: Area = r²*pi.

A Few Examples

A 50mm lens at f/2: 50mm/2 = a lens opening 25mm wide. Half of this is 12.5mm and using the equation above (pi * 12.5mm²) we get an area of 490mm².

A 50mm lens at f/2.8: 50mm/2.8 = a lens opening 17.9mm wide. Half of this is 8.95mm and using the equation above (pi * 8.95mm²) we get an area of 251.6mm².

Now, it doesn’t take a genius to work out that half of 490 is less than 251. This is because the numbers used are rounded to the nearest decimal point. The area of f/2.8 will still be exactly half of f/2.

Diagram showing what the aperture scale looks like in reality
What the aperture scale looks like in reality

How to Change Your Aperture

Now that you are aware of how the aperture is measured, we can take a look at how you can change it on your camera.

At this point, it’s important to mention that you don’t always have full control over your aperture. This happens at some so-called variable aperture lenses.

Variable Aperture Lenses

Variable aperture lenses are usually cheaper zoom lenses. The reason they are called variable aperture lenses is that the smallest aperture changes with the focal length.

Most kit lenses just like the 18-55mm f/3.5-5.6 kit lens come with a variable aperture. This means that on smaller focal lengths like 18mm you can set the maximum aperture of f/3.5. As you zoom in with the lens and reach longer focal lengths, the maximum aperture you can set will decrease.

If you reach the longest focal length, in this case, 55m, the widest aperture this lens can produce will be f/5.6.

This could be very hard to deal with as in low light conditions. When you put this into practice, you will see that even f/3.5 can be insufficient when you have less light to work with.

Let’s say the amount of light is not a problem and you would like to use a small aperture like f/11 or higher. Remember, you can set your aperture to a higher f-number regardless of the focal length.

Prime Lenses

Most professional photographers tend to use prime lenses. Prime lenses are fixed focal length lenses (this means that you can’t zoom with them). They are usually capable of very large aperture openings like f/1.4 or even f/1.2.

These are quite handy when you need to shoot in low light or want to achieve a shallow depth of field.

These lenses are usually more expensive. There could be a big price difference between two prime lenses with a difference of one single f-stop. This is because one single f-stop can make a huge difference.

Once you reach your lenses maximum aperture, you’ll only have two options to compensate for a dark exposure. One is shutter speed, and another is ISO.

Most of the time, you can’t just tweak these further, especially if you don’t have much light. Bringing up the ISO will make your image very noisy. And slower shutter speeds can make it blurry.

Check out these articles to learn everything about choosing the right shutter speed and ISO!

Now, back to the topic of how to change the aperture in your camera.

On modern digital cameras, you may have noticed that there are certain modes. These modes include “Auto”, “P”, “Tv”, “Av” and so on.

Close up of a digital camera's control dial

Full-Auto Modes

Now in Full-Auto modes, you can’t adjust any of your exposure settings. Your camera sets the optimum aperture, ISO and shutter speed for you. Remember, it always tries to compensate for a “perfect” exposure.

All digital cameras (and some film cameras) have a built-in light meter. This measures the amount of light of your scene being photographed. This light meter helps your camera to determine the right settings of your exposure.

Auto modes are not only useful for beginners. I can assure you that a lot of photography experts still use Auto modes.

Just think of event photography. Things happen really fast around you, and you need to react even faster! In situations like this, you can have a hard time dealing with continuously changing conditions.

“Tv” and “Av” Modes

Not satisfied with how your camera exposes in auto mode but still want flexibility? “Av” and “Tv” modes are for you! These modes give you the freedom to focus more on your surroundings while still keeping you in control. But how is this possible?

These two are called Aperture priority (Av) and Shutter priority (Tv) modes. Basically, you can control your priority setting depending on which mode you select. And you leave the rest to technology.

Aperture Priority (Av Mode)

In Aperture priority mode, you can set your aperture to a certain f-number. In the meantime, your camera compensates with setting shutter speed and ISO automatically. This mode is useful if the priority (as in the name of the mode) is your aperture.

Let’s say you want to achieve a certain effect. For this, you want to keep smaller apertures (like f/16 or f22).

If you choose aperture priority mode and fix your f stop, you won’t have to worry about any changing light conditions. You will get the same exposure every time you release the shutter button. Remember? You’re still in kind of a half-auto mode.

Keep in mind that if you’re shooting with such a small aperture, the compensation in shutter speed might be very radical. Your camera can even set the shutter speed close to a whole second or more.

This depends on how much light you have. All in all, aperture priority is a good choice when you have a lot of light. This way, you don’t have to worry about how your camera changes the shutter speed for you.

Aperture priority is usually used when you have a lot of light. An example could be bright, daytime landscape photography.

Shutter Priority (Tv Mode)

Shutter priority works just like the Av mode. But instead of defining your base aperture, you can fix your shutter speed. Now the ISO and aperture will be adjusted automatically. One good example of when to use Tv mode is sports events when there is a lot of movement.

The main focus when photographing an event like this is usually to capture the motion in your image. Now, this can be very difficult. Just think of a football game. Players constantly run, they move very fast and change their direction all the time. In this case, you can choose the right shutter speed to freeze their action and let your camera do the rest for you.

Manual Mode

This mode is pretty self-explanatory. In manual mode, you are in control of everything that affects your exposure. However, it takes a lot of practice and learning to really get used to the manual mode.

Before you would go out and start shooting only in manual mode, I recommend you try out the previous modes as well. This will allow you to really see how they affect your image.

How Does Aperture Affect Exposure?

By now you should probably know the answer to this question but if not, let me refresh it for you.

The change in aperture size correlates with exposure. The larger the aperture size, the more exposed the photo will be and vice versa.

The best way to demonstrate this is by taking a series of photos and keeping everything constant with the exception of the aperture.

All the images in the slideshow below were taken at ISO 200, 1/400 of a second and without a flash. Only the aperture size changes throughout.

This set of photos was taken before the recent purchase of my large aperture capable f/1.4 lens. The photos are in the following order: f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22.

Animated GIF showing changing aperture on a photo of trees

A good way to see this is to look at the size of the out of focus white circle at the bottom left of the image. The main creative effect of aperture, however, isn’t exposure, but depth of field.

How Does Aperture Affect Depth of Field?

Now, the depth of field is a big topic in photography. Apart from causing a difference in exposure, adjusting your aperture affects the depth of field. This is where things get a little bit more interesting.

What is Depth of Field?

In short, it is the distance at which the subject will stay in focus in front of and behind the main point of focus.

How Aperture Affects the Depth of Field

If you set a large aperture and take a picture, you will see that the area of focus will be very small. This is called a shallow depth of field. Keep in mind that the focal length of your lens and your distance to your subject also make a difference.

The opposite of shallow depth of field and wide aperture is a deeper depth of field. You can achieve this by setting smaller apertures like f/16 or so. Smaller apertures will produce a sharper image and a greater area of focus.

First, let’s take a look at the diagram below. If you don’t understand exactly how this works, don’t worry. The pictures below will make it clear.

For now, it’s important for you to know the effects and understand how the depth of field changes.

detailed diagram explaining how aperture affects depth of field

Here is an example of a photo taken at f/1.4. With the subject moving away from the lens, it’s easy to see the effect that the shallow depth of field has on the image.

A close up of a sports net taken with a large aperture

As mentioned, here’s a selection of photos all taken on aperture priority mode. The exposure remains constant, and the only changing variable is the aperture.

The photos in the GIF below are in this order: f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. See how the depth of field increases every time the aperture size is decreased.

Animated gif showing the same photo shot at different apertures

Diagram explaining depth of field and aperture sizes.

You can get very creative with choosing different aperture settings for changing the depth of field.

Large aperture openings can have very interesting effects on the image. Most of the time, they are used to create a soft and blurry background.

This is a nice way of separating your subject from the background. This technique can also create great depth and give a lot of mood and emotion to your image. Shallow depth of field helps the viewer to really focus on the subject, but you should be careful with it.

At very small aperture numbers like f/1.2, your area of focus can be very narrow. This means that your subject can easily fall out of focus. Even though a nice shallow depth of field can be very pleasing to your eyes, but the first priority should always be your subject.

If you choose to shoot a greater depth of field, bear in mind the issues which can come with an extremely narrow aperture (over f/22). Lens diffraction can easily ruin your final image, so we advise you to get familiar with this term.

What Are the Uses of Different Apertures?

One thing to note is that there are no rules when it comes to choosing an aperture. It depends greatly on whether you are going for artistic effect or to accurately balance the light in a scene.

To best make these decisions, it helps to have a good knowledge of traditional uses for the different aperture listed below.

  • f/1.4 – This one is great for low light situations. It also gives a shallow depth of field. Best used on a shallow subject or for bokeh effect.
  • f/2 – This range has much the same uses, but an f/2 lens can be picked up for a third of the price of an f/1.4 lens.
  • f/2.8 – Still good for low light situations, but allows for more definition in facial features due to a deeper depth of field. Good zoom lenses usually have this as their widest aperture.
  • f/4 – Autofocus can be temperamental. This is a safe aperture setting you’d want to use for portrait photography for nice and more detailed portraits. You risk the face going out of focus with wider apertures.
  • f/5.6 – Good for photos of one or two people but not very good in low light conditions though. Here, use a bounce flash if you have one.
  • f/8 – This is good for large groups as it will ensure that everyone remains in focus.
  • f/11 –  More often than not, here is where your lens will be at its sharpest. Good starting aperture for landscape photography and also high-detailed portraits of your subject.
  • f/16 –  Shooting in the sun requires a small aperture, making this a good ‘go-to’ point for these conditions.
  • f/22 –  Best for landscape photography where you want noticeable detail on your subject and the background too.

As I said before, these are only guidelines. It’s only up to you how you use this knowledge in your photography. Now that you know exactly how the aperture setting will change a photo, you can experiment yourself and have fun with it!

Common Questions

Which Aperture is Best for Portrait Photography?

I like to shoot portraits with a 50mm or 85mm lens, using a wider aperture opening like f/1.8 or so. Now if my subject is really close to the lens, I usually consider using a bit higher f-stop number like f/3.2 or even f/4. This ensures that my subject’s face is in focus and sharp.

But remember, by dialling up the aperture, your image will be darker, and you need to compensate for an evenly exposed image.

How Does Aperture Affect Bokeh?

Another creative photography effect of a large aperture is bokeh. Bokeh is basically the out-of-focus blurry background of your image. It’s the most effective when you have a very shallow depth of field and a rich background. You can see it on the below picture how the city lights create this effect in the background, behind the subject.

Which Aperture is Best for Landscape Photography?

Smaller apertures like f/8 or f/16 are usually used to create a wider focus area. This is most commonly used in landscape photography.

Just think of a scene with a lake in the foreground and mountains in the background. Here you have a great distance between the lake and the mountains, but you want to have as many things to be in focus as possible. To achieve this one, you have to set your aperture to a high f-stop number.

Think you know everything about photography? Check out our new post to see if you’re a photography nerd next! Try our Wow Factor Photography course too! 

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