A picture of flowers half in focus

What is aperture in photography?

By BBC Maestro

If you’re an aspiring photographer, it can feel like there’s a huge amount of lingo to get your head around, when all you want to do is take photos. But taking a little time to get to grips with the different terms and techniques will help you to capture even better pictures.

So, with that in mind, let’s start demystifying some of the more technical aspects by looking at what aperture is in photography.

What is aperture?

Put simply, aperture refers to the opening in a camera lens, through which light enters. It controls how much light enters your camera, which you can manually adjust. A bigger aperture gives you more light, and a smaller aperture gives less light.

It’s similar to how the human eye works. The amount of light that can reach our retinas is limited by the size of our pupils. That means that when we’re in low-light situations, our pupils become wider to let more light in.

Along with shutter speed and ISO, aperture is a crucial element of getting a properly exposed photo. These three elements are often called the ‘exposure triangle’, and the perfect balance between the three will result in a photograph with good exposure.

An eye looks into the camera

Why is aperture important?

When you adjust your camera’s aperture, there are two main things it gives you control over: exposure and depth of field.

It’s arguably the most important of the three elements of the exposure triangle in both analogue and digital photography, allowing you to control the amount of light that reaches your camera’s image sensor or film. When you adjust the aperture, you can make the image brighter or darker, depending on the conditions.

If you’re outside and the sun is particularly bright, your shot might end up being overexposed. So, in that instance, you could change the aperture so that your image isn’t too bright. On the other hand, if you’re shooting when it’s darker, you would change the aperture to let more light in, ensuring that your photograph doesn’t end up being too dark.

A person place their hand over the sun

Aperture is also important when it comes to depth of field. In simple terms, depth of field refers to how much of your image is in focus. If your image has a high depth of field, it’d mean that both the foreground and background look sharp and in focus. If you have a lower depth of field, it will mean that the main focal point of your image is sharp, while the background is blurry and out of focus.

This is related to aperture too because a wide aperture results in a shallow depth of field (where the subject is in focus and the background is blurred). You might want this effect when shooting portrait photography, for example, to ensure that the person is the main focus of your image.  

A narrow aperture increases the depth of field, meaning more of the image is in focus. You might want a large depth of field if you’re shooting landscapes, for example.

How is aperture measured?

Rather than simply saying ‘large’ and ‘small’ or ‘narrow’ aperture, you can also express it in f-numbers or f-stop values. These represent the size of the lens opening (or aperture) and you might have noticed them written on your camera’s LCD screen or viewfinder before written as f/2, f/4 or similar.

Confusingly, the smaller the f-stop number, the larger the aperture opening. That means more light enters the camera. And, conversely, the larger the f-stop number, the smaller the aperture number, and less light enters the camera.

That means that an f/2 aperture is much bigger than a smaller aperture like f/16. There’s a wide range of apertures, but most cameras’ aperture settings will include the following:

  • f/2
  • f/2.8
  • f/4
  • f/5.6
  • f/8
  • f/11
  • f/16
  • f/22

It can take a while to get the hang of, but the key thing to remember is that large apertures have a smaller number (like f/2 or f/2.8), while a small aperture has a bigger number (like f/16 or f/22).

How to choose the right aperture

Now you know what aperture is, how do you choose the right camera settings to get the perfect picture? There are a few things you’ll want to consider.

Lighting conditions

What is the lighting like? If you’re in a low-light situation, you might need a wide aperture to let more light into the camera. If you’re shooting when it’s very bright, on the other hand, you want to avoid overexposure in which case, you should choose a narrow aperture.

A street in the night

Subject and composition

What elements of your image do you want to be really sharp? Are there certain areas you want to draw attention to? This comes down to depth of field and is likely to vary depending on your style and subject matter. If you’re shooting street photography, for example, you might be aiming for a different effect than if you were taking nature photos.

If you want the subject of your photo to be clear, with a blurred background (and even some elements blurred in the foreground, too), then choose a wider aperture. Remember, that’s a small f-stop number. If you want more of the scene to be in focus, then choose a narrower aperture.

Flowers in focus

Your lenses

Different lenses work best with different apertures. It can be trial and error to figure out what works best for your particular setup – but that’s all part of the fun of photography.

camera lenses

There’s no better way to learn about different aperture settings than through practice. So, get out there and experiment – you never know what amazing images you’ll create. And if you want to find out more about the craft of taking pictures, take a look at An Introduction to Photography, our online photography course with one of the best in the business, Rankin.  

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