12 min read


What is Aperture?

Aperture is a hole within a lens, through which light travels into the camera body. If you think it as the human eye, the aperture is like the pupil of your camera, which can open and close to change the amount of light that passes through.

Together, the aperture settings, shutter speed, and ISO produce an exposure. The diameter of the aperture size changes, allowing more or less light onto the sensor.

The image below shows an aperture in a lens:

Aperture, lens, light, depth of fiel, photography

An aperture in a lens. Photo credit: Pixabay

How Aperture Affects Exposure

Aperture has many effects on your photographs. One of the most important effects that aperture has is how it alters the brightness, or exposure, of your images. As it changes in size, it modifies the amount of light that reaches your image.

A large aperture will let a lot of light get through, resulting in a brighter photograph, a small aperture will let less light get through, resulting in a darker photo.

Here’s an example of how different apertures affect exposure.

Aperture, Photography, Exposure

How Aperture affects Exposure

As you can see in this example, the smaller the f-number (large aperture), the brighter the photo, and the larger the f-number (small aperture), the darker the photo.

How Aperture Affects Depth of Field

Another aspect to consider with aperture is the depth of field (how sharp your image will be). With a small aperture, your image will be sharper, and with a large aperture, just the opposite.

A simple definition of depth of field is the distance between the closest and farthest objects in a photo that appears acceptably sharp, or in other words, how sharp your image will be.

Some pictures may have very small zones of focus which is called shallow depth of field. Others may have large zones of focus which is called deep depth of field.

With a small aperture, your image will be sharper (deep depth of field), and with a large aperture, your image will have a shallow depth of field.

A shallow depth of field is commonly used to make a subject stand out from the background and is often used for portrait photography.

Shallow depth of field can be useful in wildlife and sports photography, where you want the subject to stand out from its surroundings to bring attention to it.

Aperture, Shallow Depth of Field, Photography

Image with shallow depth of field

For the image above I used a large aperture (f/3.5), and you can see that the duck is in focus and appears sharp, while the background is completely out of focus. This helped me bring the attention of the viewer to the subject.

A deep depth of field is commonly used in landscape and cityscape photography as it is important to get as much of your scene in focus as possible.

Aperture, Deep Depth of Field, Photography,

Image with a deep depth of field

In the image above, I used a small aperture (f/11) to keep as much in focus as possible.

Here is an example that shows the difference between using a large, medium, and small aperture and how that changes the sharpness of the background.

Aperture, Photography, Depth of Field

How Aperture affects Depth of Field

I apologize for the change of perspective from one photo to another, but I didn’t have a tripod with me that day. But that’s not important since the point is to show you how different apertures change the depth of field.

As you can see, the photo from the left with an aperture of f/3.5 has a blurry background, the photo from the middle with an aperture of f/8 has a sharper background, and the photo from the right with an aperture of f/16 has an even sharper background.

How Aperture is measured?

Aperture is expressed as a number known as “f-number” or “f-stop”, for example, f/8. It is important to remember that small numbers are large apertures, and large numbers are small apertures. This could be confusing at first, but with time and practice, you’ll get used to it.

Probably, you already have noticed this on your camera. On your LCD screen or viewfinder, your aperture will look something like this: f/5.6 or f5.6.

Aperture, Photography, Fscale, Fnumber

F-stop on LCD screen

So, if you set your aperture at f/1.4, you’ll get your widest aperture, therefore, more light and shallow depth of field.

On the other hand, if you set your camera at f/22, you’ll get your narrowest aperture, therefore, less light and deep depth of field.

Why a low number for a high aperture?

That’s why when you deal with an f-number of f/11, for example, you have to think of it as the fraction of 1/11. So, a fraction like 1/11 is smaller than 1/8, therefore an aperture of f/11 is smaller than f/8.

If this is getting confusing, take a look at the image below.

Aperture Scale, camera, lens, photography, light, depth of field

Aperture Scale. Photo credit: art 209 photography

Here you can see the aperture decreases as the f-number increases.

How to set Aperture in your camera

If you want to pick your aperture manually in your camera (which is something highly recommended), there are two modes that work:

  • Aperture-priority mode, written as “A” or “Av” on most cameras, you choose the aperture and the camera automatically chooses the shutter speed.
  • Manual mode, written as “M” on most cameras, you choose both aperture and shutter speed.
Aperture, Photography, Manual Mode, Aperture Priority Mode

Manual Mode and Aperture Priority Mode

So… how do you pick the right Aperture?

Now that you understand a little better how the f-stop scale works, and the most important effects of Aperture (exposure and depth of field), we can talk about how to choose the right aperture for your photos.

Let’s say you are shooting a landscape in daylight, you’ll want to pick a small aperture like f/11 or f/16 since there’s a lot of light and you don’t want your image to be too bright or overexposed.
Regarding the depth of field, if you are shooting a landscape you’ll probably want everything in focus (deep depth of field), so with a small aperture like f/11 or f/16, you’ll get that result.

Aperture, Deep Depth of field, Exposure, Photography

Picking the right aperture

In the image above, I used a small aperture (f/11) to keep as much in focus as possible.

Now, let’s set the opposite scenario, you are taking a photo of a subject/object in a dark environment, then you’ll want to pick a large aperture like f/2.8 or f/3.5 to capture a photo of the proper brightness.
Regarding the depth of field, you’ll have a large amount of background blur, which is great for portraits.

Aperture, Shallow Depth of field, Exposure, Photography

Picking the right aperture

In the image above, I used a large aperture (f/3.5) to keep the proper brightness in a dark environment and have a blurred background so the lens ball stands out from it.

But what if you want to take a photo of a person or object, for example, in daylight, and you want a nice portrait with a shallow depth of field?

Well, here you can choose a small f-number like f/3.5.

And if you want a more shallow depth of field you could get closer to the subject, or change your focal length to a longer distance.
If you want to learn more about the 3 factors that affect depth of field, check my post “Understanding Depth of Field.”

Regarding the brightness of your photo, you can compensate that with your shutter speed or ISO.
If you want to understand more about these other two factors that affect the exposure of your photo, check my post “Get To Know Your Camera.”

Aperture, Shallow Depth of field, Exposure, Photography

Picking the right aperture

In the image above, I used a large aperture (f/3.5), and compensate the exposure with the shutter speed (1/2500), and to get a more shallow depth of field, I got really close to the fountain.

Minimum and Maximum Apertures

Every lens has a limit on how large or small the aperture can get.

If you take a look at your lens, it should specify what the maximum and minimum apertures are.

The maximum aperture will be more important because it tells you how much light the lens can pass through at its maximum or, in what low light conditions you can take photos.

That’s why lenses with large apertures usually cost more.

On the other hand, the minimum aperture is not as important as the maximum, because almost all modern lenses can get at f/16 at the minimum.

With some zoom lenses, the maximum aperture will vary as you zoom in and out.

For example, with the Canon EF-S 18-135mm f/3.5-5.6, the largest aperture changes gradually from f/3.5 at the wide end to f/5.6 at the longer focal length. More expensive zoom lenses tend to keep a maximum aperture throughout their zoom range, like the Canon EF 24-70mm f/2.8.

Prime lenses also tend to have larger maximum apertures than zoom lenses, which is one of their main benefits, like the Canon EF 85mm f/1.8.

The maximum aperture of a lens is so important that it’s included in the name of the lens itself and will change its price.

Uses of Different Apertures

The first thing you should know is that there are no rules when it comes to choosing an aperture. It depends on what you are going for in a photo, maybe you are just looking to correctly balance the light, or maybe you are going for an artistic effect.

To have a better knowledge of traditional uses for different apertures, let’s take a look at these examples.

  • f/1.4 – This is great for any kind of low light situations. It also gives you a shallow Depth of Field. Best used on portraits in a dimly-lit environment, to photograph the night sky or for a bokeh effect.
  • f/1.8 – f/2 – This range has much the same uses, but with f/2 you can get an acceptable depth of field for subjects at close distances while still producing a nice bokeh.
  • f/2.8 – f/4 – This range is 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. These apertures are great for sports, wildlife, and travel, for example.
  • f/5.6 – f/8 – This range is great for landscape and architecture photography. It is also good for large groups of people.
  • f/11 – f/16 – This range is typically used for shooting landscape, architecture, and macro photography where a deep depth of field is needed. It’s also good for shooting into the sun.
  • f/22 – Only shoot at this f-stop, or smaller when is really needed, since the image loses too much detail at this point.

Remember, this is only a guideline, so you can go out and experiment yourself with different apertures.

Aperture is a significant setting in photography and most photographers will agree it’s the most important one.

It could be confusing at first to understand how aperture works, but with practice, you won’t even have to think about it, personally I immediately know what aperture to use regarding what I’m looking for in a photo.

Go find something awesome to photograph, put into practice what you’ve learned, and have fun with it.


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