Aperture, Shutter speed, and ISO together forms the image exposure in photography. As a photographer, you must be able to control these 3 parameters according to the lighting conditions. There will be situations where you will have to use higher and lower aperture values. So, you should know the impact of different aperture values on an image. In this guide, I will show you how to set aperture for photographing different subjects.

What is Aperture?

Aperture is the opening in the camera lens through which light enters the camera. If larger the opening, more light will enter the camera and vice versa.

In the camera, it is denoted by f-number. The larger the f-number smaller will be the aperture opening and vice versa.

Each camera lens comes with maximum and minimum aperture values. The maximum possible aperture value will be written on the camera lens. A normal point-and-shoot digital camera also comes with a maximum and minimum aperture.

How to Calculate Camera Aperture?

If you are a beginner in photography, the question that comes to your mind will be, which f-number should I select for photography?

The answer to this question depends on multiple factors like the subject which you are going to shoot, whether you want a blurred background, or if you want a shallow DOF or wide Depth Of Field, etc.

Let’s see, how the f-number of a lens corresponds to the aperture opening. It can be explained better by an example.

Let’s consider the case of Canon EF 50mm f1.8 lens and Canon EF 50mm f1.4 lens. These are prime lenses (fixed focal length ones).

For Canon EF 50mm f1.8 lens, the Maximum possible Aperture opening is: 50/1.8 = 27.78 mm (diameter of the opening)

For Canon EF 50mm f1.4 lens, the Maximum possible Aperture opening is: 50/1.4 = 35.71 mm (diameter of the opening)

From the above example, it is clear that the lower the f-number, the greater will be the aperture opening.

Now, the question would be what is the use of a lower f-number? The lower the f-number, the greater the amount of light entering the camera.

It is good for low-light photography and for getting higher shutter speeds to freeze action. Also, you will get a good background blur.

👉🏻 📖 READ MORE: F-stop Chart (Aperture Stop Chart)

Aperture Vs Depth Of Field (DoF)

Aperture and Depth of Field are inversely related. The higher the aperture opening smaller will be the DoF. Since Aperture and f-number are inversely related, higher values of f-numbers correspond to a greater depth of field.

For easier understanding, have a look at the table given below:








f16 & Above

Larger DOF

More in focus



f4.0 & Below

Smaller DOF

Less in focus

Now let us see how the change in f-number affects the Depth of Field and background blur with the help of some examples.

Below given shots are taken using Canon EOS 7D with Canon EF 50mm f/1.8 lens.

The aperture value is varied from f/1.8 to f/22. The focus is on the teddy bear doll in the front. 


From the above pictures, it is clear that for getting a good background blur you will have to use a lower f-number (larger aperture opening).

For getting more things in focus you will have to use a larger f-number (smaller aperture opening).

When to Use Narrow Aperture? (Large f-number)

If you want to bring all the objects in the scene in focus, then you need to go for a narrow aperture.

Narrow aperture values are usually used by landscape photographers. Landscape photographers would want to bring foreground, middleground, and background in focus. So, they will go for a smaller aperture opening (higher f-number), usually in the range of f16 to f22.

Another point to be noted is that a higher f-number demands a slower shutter speed. You will have to keep your camera steady at slower shutter speeds by using a tripod to avoid blurry photos.

When you shoot a group of people, you will have to use a higher f-number to bring all the people within focus.

When to Use a Wide Aperture? (Small f-number)

A wide aperture is required when you do portrait photography, bird photography, sports photography, etc.

So, portrait photographers, wildlife photographers, and sports photographers will go for a wide aperture (lower f-number). The basic intention of selecting a wider aperture value is to get a nice background blur.

For wildlife and sports photography, you need to freeze the motion of the subject, which demands a higher shutter speed value. In such a situation, they will have to go for the lowest possible f-number in the camera.

Camera lenses that come with lower f-numbers are referred to as fast lenses. Now, the question is, what is this lower range of f-numbers? F-number below f/4.0 can be considered as a wide aperture. Most of these fast lenses are costly except for Canon’s EF 50mm f/1.8 lens which is also called the nifty fifty lens.

Effect of Aperture on Shutter speed, and ISO

Aperture, Shutter speed, and ISO are the three pillars of photography.

Let’s see how the change in aperture values affects the other two parameters? If you have selected a lower f-number (wide aperture opening), say f2.0; you can go for higher shutter speeds with lower ISO values. So, you can shoot your subjects handheld. Since a lower ISO value can be selected, we can reduce the noise in the image. You will be able to get a nice background blur too.

Now, select a higher f-number (narrow aperture opening), say f16.0. This value brings more objects on the scene to focus.

A higher value of f-number demands a slower shutter speed. So, you won’t be able to shoot the scene handheld.

If the lighting is too good, then you can shoot it handheld provided you choose a higher ISO value (around 1600). There will be some amount of noise in the picture. You can remove the noise during post-processing. If you intend to go for a lower ISO value, you will have to use a tripod.

Also, go through this article, ABC Of Photography, to have a better understanding of the basics of three pillars of photography.