What is Aperture in Photography, and Why Does it Matter?
You’ve probably heard about the aperture in photography, but what exactly is the aperture definition in photography? This will be a lengthy explanation, but bear with me!
Let’s start with the holy trinity of exposure:
You can adjust three exposure settings to create different effects when taking a picture. First, you must know that changing your photos’ ISO, shutter speed, and aperture will either get a darker or a brighter image. Understanding ISO, aperture, and shutter speed together is crucial!
But each of these settings has other different purposes that set them apart.
ISO is one of these settings that controls how much digital “noise” or “grain” appears in the photo. Shutter speed is another setting that affects the image, as it determines how long the camera’s shutter is open, which can result in motion blur or camera shake.
However, the aperture settings on the camera affect something else entirely – other than how bright a photo is, it determines the depth of field in the photo. Depth of field refers to how much of the image appears to be in focus.
A wider aperture (represented by a smaller f-number) will create a shallower depth of field, with only a small part of the image appearing in focus. A narrower aperture (represented by a larger f-number) will create a deeper depth of field, with more of the image appearing in focus from front to back.
For example, the photo above was taken with f/2.0, resulting in a shallow depth of field (blurred background) behind the main subject in a photo.
Definitions in Aperture Photography
This may sound incredibly confusing, so let me define some terms to untangle the chaos in your head:
An f-stop (also called an F-number) is the numerical representation of aperture. It is a term used in photography to refer to the opening in the lens through which light passes to enter the camera.
A lower f-stop value represents a larger lens opening, which allows more light to enter the camera and results in a shallower depth of field. A higher f-stop value means a smaller lens opening, which allows less light to enter the camera and results in a deeper depth of field.
The larger the f-number, the narrower the aperture is. Conversely, the smaller the f-number, the wider the aperture!
The progression of f-stops is actually based on a simple pattern: It follows a geometric sequence determined by the powers of the square root of two or the square root of the powers of two. In other words, each f-stop results from multiplying the previous f-stop by the square root of two.
Here’s how the sequence works: starting from f/1, if you multiply it by the square root of two, you get f/1.4. Then, if you multiply f/1.4 by the square root of two, you get f/2, and so on.
So the progression goes like this: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32.
Depth of Field (DOF)
A depth of field is the range of distance that appears to be in acceptable sharp focus in a photo. It is affected by several factors, including the lens aperture, focal length, and the distance between the camera and the subject.
A shallow depth of field results in a small area in the photo being in sharp focus while the rest of the image appears blurry. A deep depth of field results in a large area being in focus – from the foreground to the background.
Here is an example of different f-numbers and their irrespective depths of field (f2.0, f5.6, and f14):
“Stopping down” means to make the aperture smaller (e.g., from f/2.8 to f/5.6 or f/8); this increases the depth of field and reduces the amount of light entering the lens, which means that the shutter speed needs to be slowed down or the ISO needs to be increased to maintain proper exposure.
“Stopping up” means to make the aperture larger (e.g., from f/5.6 to f/2.8); this decreases the depth of field and increases the light entering the lens, which means that the shutter speed can be increased, or the ISO can be decreased to maintain proper exposure.
“Wide-open” shooting: In photography or videography, “wide-open” shooting uses a lens aperture set to its largest possible opening, also known as its lowest f-number.
So, in a nutshell:
A larger aperture means:
- A lower f-stop number
- A wider opening
- More light entering the camera
A narrow aperture means:
- A higher f-stop number
- A smaller opening
- Less light entering the camera
The Human Eye and Aperture in Photography
I think that the best way to understand aperture is to think about the human eye:
The pupil of the human eye is like the aperture of a camera lens. The pupil size will adjust to control the light entering the eye. In low-light conditions, the pupil will dilate or open up to allow more light to enter the eye. In bright light conditions, the pupil will constrict or become smaller to reduce the amount of light entering the eye.
Similarly, a larger aperture or wider opening in a camera will allow more light to enter the camera and create a shallower depth of field, resulting in a blurred background and a sharper subject.
Conversely, a smaller aperture or narrower opening will allow less light to enter the camera and create a deeper depth of field, resulting in a sharper background and a slightly less sharp subject.
Choosing the Right Aperture for Different Photography Scenarios
A wide aperture (a lower f-number) is useful in the following scenarios:
- When you want to achieve a shallow depth of field and blur the background, thus creating a bokeh effect.
- In natural light portrait photography, when you need all the available light but also want to separate the subject from the background.
- When shooting in low light conditions, a wide aperture lets in more light, allowing you to use a faster shutter speed and avoid camera shake.
- When you want to freeze the motion of a fast-moving subject, a wide aperture combined with a fast shutter speed can help achieve a burst effect.
- In long-exposure photography, a wide aperture can capture the subject’s movement or create light trails or paintings.
A narrow aperture (a higher f-number) is useful in the following scenarios:
- A narrow aperture for landscape images can help capture a wider depth of field, keeping the foreground and background in focus.
- In macro photography, a narrow aperture can help achieve a greater depth of field, keeping more of the subject in focus.
- To create a sunburst effect, a narrow aperture combined with a strong light source can make a starburst pattern around the light source.
- A narrow aperture in still-life and product photography can keep the subject focused and sharp.
A medium aperture is useful in the following scenarios:
- When photographing a group of people, I suggest a medium aperture that can help achieve a balance between keeping everyone in focus and blurring the background slightly.
- In low-light landscapes, you can use a medium aperture to capture a balance between the depth of field and the amount of light entering the camera.
- When photographing slow-moving wildlife, a medium aperture can help keep the subject focused while creating a pleasing background blur.
Aperture Photography FAQs
What Is the Perfect Aperture for Portraits?
Generally, a wide aperture (low f-number) is used to achieve a shallow depth of field, which can help to blur the background.
Since a wider aperture has a smaller area of focus, you need to ensure that the focus is on the subject’s eyes. The best aperture range for portrait photography is f/1.4 to f/5.6.
At What Aperture Is Everything in Focus?
The aperture at which everything in the frame is focused is called the “hyperfocal distance“.
This distance varies depending on the lens’s focal length, aperture, and distance from the subject. Typically, using a smaller aperture (higher f-number) increases the depth of field, making more of the scene appear in focus.
However, it’s important to note that using too small of an aperture can result in diffraction, which can decrease overall image sharpness.
Does a Higher Aperture Mean Less Light?
A higher aperture value (e.g., f/16) means a smaller opening in the lens, which lets in less light; this can be compensated for by increasing the ISO or slowing down the shutter speed, but both options can have drawbacks.
At What Aperture Is My Lens the Sharpest?
The aperture at which your lens is sharpest can vary depending on the specific lens you are using. Typically, you can determine the optimal aperture by starting at the widest aperture and then adjusting two to three F-stop values higher.
How to Set Aperture in Your Camera
You can alter the aperture in two ways:
- Changing the settings within the camera
- Manually rotating a specialized aperture ring located on the lens body.
What Is Aperture Priority in Photography?
There are different aperture settings or modes in your camera.
When you use aperture priority mode, the camera automatically adjusts the shutter speed to get the correct exposure for your chosen aperture setting. This is great for photographers who want control over the depth of field but don’t want to worry about the exposure settings.
When using aperture priority mode, you can adjust the ISO setting to get the desired exposure, but the camera can also do this automatically. The opposite of aperture priority mode is shutter priority mode, where you set the shutter speed, and the camera automatically adjusts the aperture camera settings.
Lastly, there is also the option of choosing manual mode for adjusting the aperture camera setting. In manual mode, photographers will have complete creative control over their images. This mode requires a good understanding of the relationship between aperture, shutter speed, and ISO (though you can choose this setting to be auto). All these settings must be adjusted together to achieve a properly exposed image.
Types of Lenses and Aperture
Some lenses have a fixed aperture, while others have a variable aperture.
Prime and high-end zoom lenses have a fixed maximum aperture across all focal lengths, while lower-end zoom lenses have a variable maximum aperture. A variable aperture lens is a type of camera lens that can change its aperture size as the zoom changes.
Lenses with larger maximum apertures are often called “fast” lenses. These lenses are great for low-light situations and can create a shallower depth of field, making the subject stand out more. I also believe they are more performant optically.
Examples of fast lenses include (large-aperture lenses):
Aperture Photography Pro Tips
- Use aperture priority mode. This can be an excellent way to experiment with different apertures while ensuring proper exposure.
- Aperture affects not only the depth of field but also the amount of light entering the camera. If you’re shooting in bright sunlight and want a wider aperture, you may need a neutral density filter to avoid overexposure.
- To check how much of your image is in focus, use the depth of field preview button on your DSLR camera. This button stops the aperture while pressed, allowing you to see the level of blurriness in the foreground or background. The button is often found near the lens on the front of most camera bodies.
- When calculating the aperture, it’s also essential to consider the distance between the camera and the subject. This is because the closer you are to the subject, the shallower your depth of field will be, even with a smaller aperture.
- A polarising filter is a type of filter that can be attached to your camera lens to reduce glare and reflections in your photos. If you’re using this, be mindful that it can reduce the light entering your camera by up to 2 stops, meaning you may need to use a wider aperture to compensate for the reduced light.
- Experiment with different apertures on your lenses to find the sweet spot for sharpness and quality.
My opinion is that the aperture is non-arguably the most critical setting in the exposure triangle. But aperture isn’t just about getting the right exposure or creating beautiful bokeh; it’s also a tool for creative expression.
By adjusting the depth of field, you can draw attention to specific elements in the frame or create a sense of depth. It’s an essential component of visual storytelling that can help you convey emotion, mood, and meaning through your images.
To learn more about using exposure settings in your photography, check out The Basics of Photography section.