What is Camera Aperture in Photography?

Camera aperture is a photographer’s most important creative tool; it determines how much light comes through your lens.

The aperture is vital to the exposure triangle (shutter speed, ISO and aperture). When a camera takes a photo, the shutter mechanism opens, and light comes on to the sensor, after which the shutter closes again. When the lens hits the sensor, and you have a lens attached to your camera, the light goes through the lens first.

1. Definition

The aperture is the opening of a lens’s diaphragm through which light passes to enter the camera. In photography, the “pupil” of your lens is called the aperture. You can shrink or enlarge the size of the aperture to allow more or less light to reach your camera sensor. Aperture is calibrated in f/stops and is generally written as numbers such as 1.4, 2, 2.8, 4, 5.6, 8, 11 and 16.

2. What are a Large and a Small Aperture?

A large aperture is a wide lens opening, allowing it to capture more light. This is also called low ranging. It is related to low F-stop values, usually ranging from f/1.4 to f/4.

A small aperture is an opposite: a narrow lens blade opening that doesn’t allow the passage of much light. It’s also called a high aperture. It is related to high  F-stop values ranging from f16 to f22.

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 recommend using something like f/8, f/11, or f/16.

3. How does Aperture Affect Photography

We have established that aperture influences the amount of light you capture with your camera; how does it translate visually in your photographs? Aperture affects depth of field, Sharpness, and exposure.

3.1 How Aperture Affects Depth of Field

The depth of field is the proportion of the image that is reasonably sharp and in focus from front to back. Some photos have a “thin” or “shallow” depth of field, where the background is entirely out of focus. Other images have a “large” or “high” depth of field, where both the foreground and background are sharp.

The lower the f/stop—the larger the opening in the lens—the less depth of field—the blurrier the background.

The higher the f/stop—the smaller the opening in the lens—the greater the depth of field—the sharper the background.

The aperture and depth of field that you have to look for depend mainly on the following:

• The scene that you’re photographing

The type of scene you want to capture will usually dictate if you require less or more depth of field.

For instance, if you’re photographing landscapes, you’ll probably aim at having as much of the image in focus as possible, whereas if you’re shooting portraits, your goal might be a blurred background, so all the attention goes to the subject.

• Your artistic view

From an artistic point of view, there is no rule to determine the depth of field and aperture in your image.

For example, you can intentionally leave the foreground of your landscape out of focus to lead the viewer’s eye to the background. Or, in a portrait, shoot everything in focus because the background says something important, too.

3.2 How Aperture Affect Exposure

Exposure refers to the brightness of a photo. Aperture is one of the three key variables that affect your exposure. (The other two variables are shutter speed and ISO). As the 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 much light, resulting in a brighter photograph. A small aperture does just the opposite, making a photo darker.

So if you’re photographing a beautiful sunset and your photos turn out too bright, you can always narrow the aperture to darken the image.

On the contrary, in low lighting conditions (golden and blue hours, overcast days etc.), you may want to use larger apertures to avoid underexposing your photographs.

3.3 How Aperture Affect Sharpness

Aside from exposure and depth of field, the Aperture also affects sharpness, but differently.

Lenses perform best when they are at their sharpest. Sharpest meaning where all the lines and parts with contrast are the sharpest, not the focus plane of the photo.

When you use a very large aperture, your lens can’t physically produce the sharpest results since the diaphragm will be wide-open, trying to capture as much light as possible.

That way, as you open your aperture below f/5.6 values, you’ll be able to notice how your image loses sharpness.

4. Which Aperture is Best? Bigger vs. Smaller Aperture

One of the most common questions in photography is which is the best aperture? Shall I use a big or a small aperture?

Well, there is no black-and-white answer, and your choice will depend on the type of photography you’re taking and your artistic goals.

4.1 Aperture for Portraits

We separate our subject from the surroundings for classic portraiture by using “selective focus.” Choosing a large aperture (lower f/stop, like f2.8) creates a very shallow depth of field with only the subject, or just a portion of the subject, in focus. This helps direct the viewer’s attention to the subject.

4.2 Aperture for Landscape Photography

When choosing lenses for landscape photography, we usually want to see as much detail as possible from foreground to background; we want to achieve the maximum depth of field by choosing a small aperture (higher f/stop, like f/8 or f/11