(Last updated on July 28th, 2022)
The aperture is a pillar of exposure and is essential in all aspects of photography. This is why it is a necessary setting to master and understand.
The concept of aperture and photography can be a little confusing. In this article, I will walk you through what the aperture is and how it affects an image. With these tools, you will create stronger photographs.
In addition, with this knowledge, you will have the tools needed to make decisions about what aperture to use. So let’s go!
What is Aperture in Photography?
The aperture is the physical opening of the lens. It is the first point where light can be controlled in a camera. This is why it impacts exposure.
The best way to think about it is by thinking about our own eyes. Our pupils dilate or open up when we enter a dark room. This allows more light to hit the retina and allows us to see in lower light.
A lens’ aperture also can open up in a low light situation. This allows more light to pass through the lens and expose the image. Conversely, you can stop down the aperture and decrease the amount of light that makes it through the lens. Just as our pupil constricts when we step outside on a bright sunny day.
The key to remember is the larger the aperture opening means more light enters the camera. And vice versa.
Focal Stop
Apertures are determined by setting the f/stop. This is short for focal stop. It determines how much of the scene will be in focus. It uses a numbered system that at first can be confusing but bear with me, it is important to understand.
The smaller the f/stop, the larger the aperture.
The larger the f/stop, the smaller the aperture.
It is an inverse relationship.
A trick I use to help remember is by thinking of the photography group f/64. This group of landscape photographers included Ansel Adams. Landscape photography requires the largest depth of field, something achieved with a smaller aperture, such as f/64.
Thus f/1.4 is a larger opening, allowing more light to enter the camera, and reducing the depth of field.
However, f/16 is a smaller opening, reducing the amount of light and increasing the depth of field.
What Does the Aperture Do?
In the simplest terms, the aperture controls how much light enters the camera and how much of the image will be in focus once it lands on the sensor.
Exposure
Since it controls light, it is part of the exposure triangle. This is the key to exposure in digital photography. It is composed of the aperture, the shutter speed, and the ISO.
A large aperture (and smaller f/stop number) will let more light in, creating a brighter image.
A smaller aperture (and larger f/stop number) constricts the light, creating a darker image.
I hope with these examples you are starting to see the connection, and importance, of the aperture and exposure.
Depth of Field
Remember, the f in f/stop stands for focal. This is because the f/stop controls the focal range of a lens. That is to say how much of the scene will appear in focus. This is known as the depth of field.
While there is only one true plane of focus, the aperture helps create a perceivable area of focus in a scene.
Let’s experiment.
Take a few deep breaths. Try to relax and be as calm as possible. Next, dilate your eyes. You can do this by not focusing on anything. Once your vision goes blurry, your pupils have dilated, i.e. reduced the f/stop of your eyes.
Nothing is in focus. Find an object on the other side of the room and quickly squint and direct your eyes there. Everything snaps back into focus. You stopped down your pupils, i.e. increased the f/stop of your eyes.
Camera lenses work the same way. The larger the aperture, the shallower the depth of field. The smaller the aperture the larger the depth of field.
What Aperture Does to an Image
Beyond controlling the depth of field and exposure, the aperture causes many other effects. Some effects are wanted and used to build a stronger composition. While photographers will do everything in their power to avoid some of the other effects.
Diffraction
Diffraction is part of every lens. When you stop down your aperture to an aperture of f/22 or greater, you are forcing the light to squeeze through a tiny hole.
Because of this, the light ends up interfering with itself. In practice, this reduces the sharpness of the overall image.
Smaller sensors also impact diffraction. If you are using an APS-C or crop-sensor, diffraction will be more noticeable.
Every lens is different and it is best to read about your lens and find the best f/stop. This is known as the sweet spot. For most lenses, it is usually f/8 or f/11. This provides the greatest depth of field while reducing diffraction effects.
Aberrations
Aberrations are image quality problems caused by the lens. No lens is perfect. There are several types and this article would be far too long to explore them in detail. Some examples include vignetting, spherical aberration, field curvature, coma, distortion, and chromatic aberrations, among others.
It is important to know why they occur and how to work with them. Glass is the optically clearest when flat. However, the elements in a lens are curved to bend the light towards the sensor. This curvature manifests in any number of aberrations.
When you stop down a lens and use a smaller aperture, you can reduce the number of aberrations in your image. This is because light from the sides of the lens will be blocked. Meaning the light must pass through the center part of the elements.
This is usually the flattest part of the glass.
Starbursts and Sunstars
This effect is one of my favorite tools. It can turn a so-so image into a captivating creation.
When using a smaller aperture and including the sun, or other bright points of light, you can create a star-like effect in your image. The trick is to use something to just barely block the light source, like the rock in the below image.
The number of blades that build the aperture determines how many rays the starburst will have. If you have 10 blades, there will be 10 points. If you have an odd number, say nine blades, there will be 18 points.
Each blade creates one of the points we see in a starburst. However, an even amount will overlap with each other due to the symmetry of the aperture.
Bokeh
This is one of the prized effects of aperture. It is accomplished with a wide-open aperture, usually greater than f/4. When points of light are out of focus, they take on the shape of your aperture opening.
This can be a pleasing effect in many genres of photography, from portrait to landscape.
The key to remember is the bokeh will take on the shape of the aperture opening. Generally speaking, the wider the aperture, the more round it appears.
How to Change the Aperture
Refer to your camera’s manual to find the aperture dial. Most digital cameras today, both DSLR and mirrorless cameras, have a dedicated aperture dial on the top of the camera body.
I highly recommend setting your aperture manually. You can do this by selecting the manual mode and controlling the entire exposure yourself. Or use Aperture-Priority mode. This will allow you to determine the aperture and the camera to determine the shutter speed.
I use Aperture-Priority, or Av mode most of the time. Typically, I select the A mode on the setting dial and leave my ISO at the native, or base ISO. This allows me to only adjust the shutter speed.
As a street photographer, the aperture choice can shift from one image to the next. Being able to quickly adjust the f/stop is critical to documenting individual moments on the streets.
When using manual mode, or the M on the setting dial, you have control over all three aspects of the exposure triangle. The ISO, the shutter speed, and the aperture. This allows for full creative flexibility. I use it predominantly in landscape photography when I need to be as precise as possible with the exposure.
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The Faster the Lens, the Less Light Required
Now that you know the basics of aperture photography, you can be better informed when purchasing a new lens.
The f/stop is part of a lens’ name. This number associated with the lens title is the maximum aperture the lens is capable of, meaning the largest opening.
A fast lens has a f/stop of f/2.8 or less. These lenses are great for low-light photography, including astrophotography.
While these lenses can still thrive at smaller apertures, the minimum aperture of a lens is less important. Mostly this is due to the increase in aberrations at higher f/stops.
Many zoom lenses have a maximum aperture range, like the Nikon 18-55mm f/3.5-5.6. As you increase the size of the aperture opening, lens elements need to be larger and heavier. By creating a range, lens manufacturers can create a happy middle-ground of quality and size.
This also helps keep costs down. Zoom lenses with a constant maximum aperture are more versatile in low-light but do cost more, such as the Nikkor Z 24-70mm f/2.8 S.
Which Aperture is the Best
Determining the aperture that is best for a given image is one of the more enjoyable parts of photography. It gives you, the photographer, a breath of creativity. It is the first step in developing your personal style.
Let’s explore some popular genres of photography and what aperture is best for each one. However, a guideline to remember is that the best aperture is the one that will allow the image to be created in the first place.
Landscape
Remember the f/64 group from earlier? These landscape photographs were focused on creating images with as much of the scene in sharp focus as possible. Hence, they relied on the aperture of f/64 with their large format cameras.
Digitally speaking, however, I rarely set the aperture to f/22 for my landscape photography. I typically use anything between f/8 and f/16. This number fluctuates with whatever lens I am using.
The concept is to get the light to pass through the flattest portion of the glass elements to create crisp, sharp, and aberration-free images.
Portrait
Portrait photography is about the subject, or person in the frame. You want to separate them from the background and direct the viewer’s eye towards them. Using a shallow depth of field, created with a larger aperture, will achieve this separation.
Many portrait photographers use an 85 mm prime lens. Prime just means a fixed focal length. The maximum aperture is usually always greater than f/2.8.
Focus on the subject and the background will fall out of focus. This creates a soft background and emphasizes the person.
Street
Street photography is a fast-paced genre. The moments are fleeting. This is why I choose the Aperture-Priority mode. Each image has a different aperture setting that is determined by the subject matter.
If I am creating a candid portrait, I tend to open up my lens and create separation between the background.
A person walking in the shadows. Using a smaller aperture here allowed the entire scene to be in crisp focus.
If it is a bright sunny day with harsh shadows, I prefer a wider depth of field to accentuate the contrast and details of a scene.
Street photography and aperture photography go hand-in-hand. Together they are a perfect way to practice and improve your photography.
Macro
Macro photography is another genre where subject matter determines the aperture. Some macro photographers prefer an extremely shallow depth of field to highlight tiny details of a miniature world.
With macro lenses, the depth of field is smaller, even at higher f/stops. So many photographers prefer to use an aperture of f/5.6 or f/8 to be sure the subject is in focus.
F/8 and Be There
This is a common phrase in photography made popular by the famous street photographer, Arthur Fellig, also known as Weegee. The aperture f/8 was the best choice for the early film cameras he used. It provided crisp sharpness and a wide depth of field.
Though lenses have vastly improved since Weegee’s time on the streets, f/8 is still a go to aperture. Using this aperture will reduce the amount of aberrations in your images as the light is forced to pass through the best optical part of the lens elements.
The second part of this phrase is the most important. You cannot create photography if you are not there. Now that you have this aperture photography basic concepts down, grab your camera and hit the streets. Or find a subject to document. Go create.
Frequently Asked Questions
The aperture is the size of the opening in the lens when the image is created. Referred to as the f/stop.
Aperture impacts the image in two prominent ways. It determines how much light enters the camera, affecting exposure. It also determines the depth of field, or how much of the image is in focus.
The aperture affects the shutter speed due to its role in creating proper exposure. With a smaller aperture or higher f/stop number, more light is needed so the shutter speed must be slower to allow more light to enter the camera.
The maximum aperture of a lens is the widest aperture possible. This is always noted on the outside of a lens.
The best aperture for portrait photography is a wider f/stop, such as f/2.8.
For landscape photography, the best aperture to use is typically f/11 or f/16.
Richard Bednarski is a freelance writer, photographer, and videographer. Photography is his passion and he draws from my experiences as an archaeologist and a father of two in order to connect with communities. He also holds a master’s degree in Media Innovation.
Richard has focused his career on documenting the American West and human stories while also writing about photography. When not writing stories that matter, Richard can be found traveling and camping with his wife and two daughters, tending a garden, baking bread, and playing the banjo.
