Understanding aperture is absolutely critical if you want to take the best possible photos. Along with Shutter Speed and ISO, it is one of the three pillars of photography – and almost certainly the most important.
Aperture can add dimension to your photos by controlling depth of field. At one extreme, aperture gives you a blurred background with a beautiful shallow focus effect. At the other, it will give you sharp photos from the nearby foreground to the distant horizon. On top of that, aperture also alters the exposure of your images by making them brighter or darker.
What is Aperture in Photography?
Aperture is a hole within a lens, through which light travels into the camera body. It is an easy concept to understand if you just think about how your eyes work. As you move between bright and dark environments, the iris in your eyes either expands or shrinks, controlling the size of your pupil. In photography, the “pupil” of your lens is called aperture. You can shrink or enlarge the size of the aperture to allow more or less light to reach your camera sensor. The image below shows an aperture in a lens:
The technical definition of aperture is: “The opening in a lens through which light passes to enter the camera.”
How Aperture Affects Exposure
Aperture has several effects on your photographs. One of the most important is the brightness, or exposure, of your images. As aperture changes in size, it alters the overall amount of light that reaches your camera sensor – and therefore the brightness of your image. A large aperture (a wide opening) will pass a lot of light, resulting in a brighter photograph. A small aperture does just the opposite, making a photo darker. Take a look at the illustration below to see how it affects exposure:
In a dark environment – indoors, or at night – you will probably want to select a large aperture to capture as much light as possible. This is the same reason why your pupils dilate when it starts to get dark.
How Aperture Affects Depth of Field
The other critical effect of aperture is depth of field. Depth of field is the amount of your photograph that appears sharp from front to back. Some images have a “thin” or “shallow” depth of field, where the background is completely out of focus. Other images have a “large” or “deep” depth of field, where both the foreground and background are sharp.
In the image above, only the word “Cougar” is in focus due to my careful choice of aperture. Specifically, I used a large aperture here, which naturally results in a shallow focus effect. If I had chosen a much smaller aperture, the entire photo from front to back might have appeared sharp, without any clear out-of-focus background.
One trick to remember this relationship: a large aperture results in a large amount of background blur. This is often desirable for portraits, or general photos of objects where you want a blurry background. For example, one reason why the photo below works well because it has a blurry background (and pleasing bokeh):
On the other hand, a small aperture results in a small amount of background blur, which typically is ideal for things like landscape and architectural images. In the landscape photo below, I used a small aperture to ensure that both my foreground and background were as sharp as possible from front to back:
And here is a quick comparison to show the two side by side:
What Are F-Stop and F-Number?
So far, we have only discussed aperture in general terms like large and small. However, it can also be expressed as a number known as an “f-number” or an “f-stop.”, with the letter “f” appearing before the number, like f/8.
Most likely, you have noticed this on your camera before. On your LCD screen or viewfinder, your aperture will look something like this: f/2, f/3.5, f/8, and so on. Some cameras omit the slash and write f-stops like this: f2, f3.5, f8, and so on. For example, the camera below is set to an aperture of f/8:
So, f-stops are a way of describing the size of the aperture (how open or closed the aperture blades are) for a particular photo.
Large vs Small Aperture
There’s a catch – one important part of aperture that confuses beginning photographers more than anything else. This is something you really need to pay attention to and get correct: Small numbers represent large, whereas large numbers represent small apertures.
That’s not a typo. For example, f/2.8 is larger than f/4 and much larger than f/11. Most people find this awkward, since we are used to having larger numbers represent larger values. Nevertheless, this is a basic fact of photography. Take a look at this chart:
This causes a huge amount of confusion among photographers, because it’s completely the reverse of what you would expect at first. However, as strange as it may sound, there is a reasonable and simple explanation that should make it much clearer to you: Aperture is a fraction.
When you are dealing with an f-stop of f/10, for example, you can think of it like the fraction 1/10th. Hopefully, you already know that 1/10th is clearly much smaller than a fraction like 1/2. For this exact reason, an aperture of f/10 is smaller than f/2. Looking at the front of your camera lens, this is what you’d see:
So, if photographers recommend a large aperture for a particular type of photography, they’re telling you to use something like f/1.4, f/2, or f/2.8. And if they suggest a small aperture for one of your photos, they’re recommending that you use something like f/8, f/11, or f/16.
How to Pick the Right Aperture
Now that you’re familiar with some specific examples of f-stops, how do you know what aperture to use for your photos? Let’s jump back to exposure and depth of field – the two most important effects of aperture. First, here is a quick diagram to demonstrate the brightness differences at a range of common aperture values:
Or, if you’re in a darker environment, you may want to use large apertures like f/2.8 to capture a photo of the proper brightness (once again, like when your eye’s pupil dilates to capture every last bit of light):
As for depth of field, recall that a large aperture value like f/2.8 will result in a large amount of background blur (ideal for shallow focus portraits), while values like f/8, f/11, or f/16 will help you capture sharp details in both the foreground and background (ideal for landscapes, architecture and macro photography).
Don’t fret if your photo is too bright or dark at your chosen aperture setting. Most of the time, you will be able to adjust your shutter speed to compensate – or raise your ISO if you’ve hit your sharp shutter speed limit.
Here is a quick chart that lays out everything we’ve covered so far:
|Aperture Size||Exposure||Depth of Field|
|f/1.4||Very large||Lets in a lot of light||Very thin|
|f/2.0||Large||Half as much light as f/1.4||Thin|
|f/2.8||Large||Half as much light as f/2||Thin|
|f/4.0||Moderate||Half as much light as f/2.8||Moderately thin|
|f/5.6||Moderate||Half as much light as f/4||Moderate|
|f/8.0||Moderate||Half as much light as f/5.6||Moderately large|
|f/11.0||Small||Half as much light as f/8||Large|
|f/16.0||Small||Half as much light as f/11||Large|
|f/22.0||Very small||Half as much light as f/16||Very large|
Setting Your Aperture
If you want to select your aperture manually for a photo (which is something we highly recommend), there are two modes which work: aperture-priority mode and manual mode. Aperture-priority mode is written as “A” or “Av” on most cameras, while manual is written as “M.” Usually, you can find these on the top dial of your camera (read more also in our article on camera modes):
In aperture-priority mode, you select the desired aperture, and the camera automatically selects your shutter speed. In manual mode, you select both aperture and shutter speed manually.
Maximum and Minimum Aperture of Lenses
Every lens has a limit on how large or how small the aperture can get. If you take a look at the specifications of your lens, it should say what the maximum and minimum apertures are. For almost everyone, the maximum aperture will be more important, because it tells you how much light the lens can gather at its maximum (basically, how dark of an environment you can take photos). A lens that has a maximum aperture of f/1.4 or f/1.8 is considered to be a “fast” lens, because it can pass through more light than, for example, a lens with a “slow” maximum aperture of f/4.0. That’s why lenses with large apertures usually cost more.
In contrast, the minimum aperture is not that important, because almost all modern lenses can provide at least f/16 at the minimum. You will rarely need anything smaller than that for day-to-day photography.
With some zoom lenses, the maximum aperture will change as you zoom in and out. For example, with the Nikon 18-55mm f/3.5-5.6 lens, the largest aperture shifts gradually from f/3.5 at the wide end to just f/5.6 at the longer focal lengths. More expensive zooms tend to maintain a constant maximum aperture throughout their zoom range, like the Nikon 24-70mm f/2.8. Prime lenses also tend to have larger maximum apertures than zoom lenses, which is one of their major benefits.
The maximum aperture of a lens is so important that it’s included in the name of the lens itself. Sometimes, it will be written with a colon rather than a slash, but it means the same thing (like the Nikon 50mm 1:1.4G below).
Examples of F-Stop Use
Now that we have gone through a thorough explanation of how aperture works and how it affects your images, let’s take a look at different examples of f-stops and when they are commonly used. Please keep in mind that the below are simply examples of what you can do at different f-stops – their use can extend far beyond with different types of photography.
- f/0.95 – f/1.4 – such “fast” maximum apertures are only available on premium prime lenses, allowing them to gather as much light as possible. This makes them ideal for any kind of low-light photography when photographing indoors (such as photographing wedding receptions, portraits in dimly-lit rooms, corporate events, etc). With such wide f-stops, you will get very shallow depth of field at close distances, where the subject will appear separated from the background.
- f/1.8 – f/2.0 – some enthusiast-grade prime lenses are limited to f/1.8 and offer slightly inferior low-light capabilities. Still, if your purpose is to yield aesthetically-pleasing images, these lenses be of tremendous value. Shooting between f/1.8 and f/2 typically gets adequate depth of field for subjects at close distances while still yielding pleasant bokeh. In addition, some wide-angle prime lenses perform great when stopped down to f/1.8 – f/2 range when doing astrophotography, such as when photographing the Milky Way.
- f/2.8 – f/4 – most enthusiast and professional-grade zoom lenses are limited to f/2.8 to f/4 f-stop range. While they are not as capable as f/1.4 lenses in terms of light-gathering capabilities, they often provide image stabilization benefits that can make them versatile, even when shooting in low-light conditions. Stopping down to the f/2.8 – f/4 range often provides adequate depth of field for most subjects and often yields superb sharpness.
- f/5.6 – f/8 – this is the ideal range for landscape and architecture photography. It could also be a good range for photographing large groups of people. Stopping down lenses to the f/5.6 range often provides the best overall sharpness for most lenses and f/8 is used if more depth of field is required.
- f/11 – f/16 – typically used for photographing landscape and architecture where as much depth of field as possible is needed. Be careful when stopping down beyond f/8, as you will start losing sharpness due to the effect of lens diffraction.
- f/22 and Smaller – only shoot at such small f-stops if you know what you are doing. Sharpness suffers greatly at f/22 and smaller apertures, so you should avoid using them when possible. If you need to get more depth of field, it is best to move away from your subject or use a focus stacking technique instead.
Aperture is clearly a crucial setting in photography and it is possibly the single most important setting of all. That’s because depth of field and exposure have such major effects on an image, and your choice of aperture changes both of them. Aperture also has a number of other effects that are too extensive to fit in this article. Check out this article for a lot more information on this topic.
Knowing how important aperture is, it shouldn’t be a surprise that, at Photography Life, we shoot in aperture-priority or manual mode most of the time. We practically never want the camera to select the aperture for us. It’s just too important, and it is one of those basic settings that every beginner or advanced photographer needs to know in order to take the best possible images.
Hopefully, you found that this article explains the basics of aperture in a way that is understandable and straightforward. The next important camera setting to learn is ISO, which we explain in Chapter 5 of our Photography Basics guide.