Aperture in Photography. What it is and how to use it?

Last Updated on December 30, 2021 | In Photography Tips by Stefano Caioni Leave a Comment

Aperture is one of the most important concepts in photography.

Together with shutter speed and ISO, it’s one of the three pillars that form the exposure triangle.

Learning what is the aperture is key if you want to up your photography game. Get excited because today you’ll learn what the aperture is, how it affects your images, how it impacts the highlights and the shadows, and last but not least how it affects the depth-of-field. 

lens aperture

In this post, you’re going to learn everything you need to know about aperture and how to use it in no time.

Read also: How aperture helps creating a black background.

How Aperture Works

Before we jump straight into the details, let me make a few points

Aperture Definition

The aperture of a lens is the size of the opening that allows light through into the camera body.

How to Measure the Aperture

Aperture is measured in f-stops or f-numbers (e.g. f/2, f/4 … f/22, etc.)


The Effect of Aperture on a Photograph

The aperture affects the brightness (exposure) and the depth-of-field on a photo.

When taking a photo, your lens diaphragm opens up for a certain amount of time (exposure time), and it allows the light to hit the camera sensor and record the image.

The size of the lens opening is the aperture, and it’s measured in f-stops. More on f-stops down below.

It’s essential to understand quickly that mastering this camera setting will allow you not only to improve your photos dramatically, but it will open the door to mastering the depth-of-field and take your expertise to the next level. 

Related on Pixinfocus:

Measuring Aperture: F-Stop or F-Number

Let’s now introduce the concept of f-stop and how to measure aperture.

You might have noticed before that your camera viewfinder displays some numbers such as f/2, f/5.6, f/11, and so on. Those are f-stops and describe the size of the aperture.

Take a look at the chart and find the catch.

aperture chart

Yes, you’re right, that’s not a mistake. The smaller the f-number the larger is the aperture. The bigger the f-number the smaller the aperture. And that’s something that confuses a lot of photographers in the beginning, but it’s a super important thing to get right from the start.

In the example below, you can see how the aperture affects the brightness of an image (exposure).

brightness example

From left to right, the initial “small” value of f/2.8 allows more light to enter the camera and hit the sensor. That’s a wide or large aperture. Moving forward, reducing the aperture reduces the brightness, and as you notice, the values on the second and last images are f/8 and f/22.

So again, the bigger the f-number, the smaller the aperture, and the darker the image, the smaller the f-number, the larger the aperture, and the brighter the image.

Aperture and Depth of Field

The depth-of-field is the distance between the nearest and the farthest objects that appear to have acceptable sharpness in an image.

In the following chart, you can see how aperture affects depth-of-field.

aperture and depth of field

Let’s see an example:

depth of field example

On the left, a wide-open lens (f/2.8) results in a shallow depth-of-field. The background is out of focus and the main subject stands out more. 

On the right, a small aperture (f/16) produces a deep depth-of-field and the result is an image with a sharp background and foreground.

This image will clarify even more.

aperture and depth of field

There’s a lot more to say in regards to the depth-of-field and how to master it with the knowledge of Hyperfocal Distance. Read more here Depth of Field and Hyperfocal Distance.

Aperture Mechanism and More Examples

By adjusting your camera settings, you affect a series of circular blades inside your lens. The blades will narrow down and widen up, determining different opening, according to the values you choose.

night photograph

In night cityscape photography, a value of f/16 or f/22 creates that interesting star effect when shooting bright spotlights, as you can see in the image above.

If you’re shooting landscapes, the sun will be an excellent subject to experiment with. The best time of the day for this is either going to be sunrise or sunset.

narrow aperture in a landscape photograph

A wide aperture will cause a smooth background effect called bokeh.

Bokeh caused by wide aperture

Exit Auto Mode

How to set different your camera properly? I recommend to abandon the auto mode of your camera and set it to Aperture Priority mode. It’s called A (or Av on Canon cameras). 

The Aperture Priority mode is a semi-manual mode with which you can adjust the aperture value, and the camera will automatically determine the correct shutter speed for a proper exposure. 

The Complete Guide to Camera Settings will walk you through the process step by step in case you need it.

Aperture Examples in Landscape Photography

In landscape photography, you want to make sure that your entire scene is in focus. For this reason, you will select a large f-number.

By setting your camera to aperture priority mode, the camera itself will take care of ISO and shutter speed. Here’s an example.
With a small aperture (f/20) I was able to get most of the image in focus.

Roys Peak NZ Olympus M.Zuiko 12-40mm f/2.8

Sharp Lenses (Zoom and Prime)

Now that you know more about this fundamental concept, if you’re looking for a new lens check out these fast f/1.8 Prime lenses:

And some zoom lenses if you want more flexibility to compose your images.

Aperture, Video Explanation

I found this video on Fstoppers and I thought I might include it here if you want a nice graphical explanation of how aperture works.

As you can see in the video at:

0:13 Definition: it’s the hole in the lens through which light travels into the camera body and onto the camera sensor.

1:00 The diaphragm is the “iris” of the lens and controls the size of the aperture.

1:10 It is expressed in F-stops or F-numbers. Small f-stop = large aperture. Large f-stop = small aperture.

1:42 It has a direct impact on the Depth of Field: the area of the image that appears sharp.

2:20 Fast Lenses description. F1.4 to F2.8 are considered fast lenses.

2:55 Prime and zoom lenses

3:40 How it affects ISO and Shutter speed

4:34 Set your camera to aperture priority mode

Further Readings

At his point, you know quite a lot about this topic. To master it, make sure to experiment with different values and scenarios and with different compositions

Exploring the menu of your DSLR or mirrorless camera and playing around with different settings is one of the most important things to do when learning photography. 


Let me know in the comments below if you have any questions or need any help understanding how your camera works!

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