Canon Aperture

Canon 85mm f1.8 Lens Photo at Maximum ApertureCanon Lens Aperture

Camera settings can be confusing, but this basic guide to Canon camera aperture will help you slice through the confusion. This post will help you understand what an aperture setting on your Canon camera is, what aperture priority mode is and explain why aperture is so important to control.

This post also includes a Frequently Asked Questions section (FAQ) and a short video from Canon that gives you a great explanation of aperture. 

Knowing how and why to change aperture settings on your Canon will help you improve your photography and take better photos, and we all want that. First, we look at what lens aperture is.

What Is Aperture On a Canon Camera

Aperture is the size of the lens opening when light is allowed to pass through the lens, enter your camera and strike the sensor. Smaller apertures let less light into the camera and larger lens openings let in more light. We use f/stop numbers to describe the specific sizes of the lens opening.

F/stop numbers are at first confusing, but are easier to understand if you remember this one thing. Smaller apertures have bigger numbers and larger apertures have smaller numbers. That seems up side down, but f/stops area actually fractions. 

You can think of it this way. The fraction 1/4 (f/4.0) is larger than the fraction 1/16 (f/16).

Aperture Scale

To help you see how aperture and f/stop number are related look at the diagram below. If no other camera settings are changed at the same time, you can see that exposure goes up with larger apertures.

Canon aperture scaleSmaller "f-stop" numbers are larger apertures.
An f/4 lens opening is much larger than an f/16 lens opening.

Why Aperture Is So Important

Aperture is important for several reasons. It makes a big difference in how much light can enter into your camera through the lens.

DEPTH OF FIELD. Using smaller apertures gives you greater depth of field, meaning more distance behind and in front of your focusing point will be in sharp focus as well.

 how aperture affects depth of fieldHow aperture affects depth of field

SHUTTER SPEED.  Aperture choice affects what shutter speed you use. If you narrow the lens opening, you'll have to use a slower shutter speed to allow enough light in for a proper exposure.

IMAGE QUALITY. Depending on the specific lens you're using, lenses do produce some loss of image quality and both ends of the aperture scale.

Adjusting The Aperture

If you've already done a little research on camera settings with your Canon, you've likely seen terms such as stopping down or opening up with regards to your Canon's aperture. Stopping down means reducing the light passing through your lens and opening up means enlarging the opening.

There are several different ways to set aperture and control the size of the opening in your Canon camera lens. The size affects how much light can enter the camera and hit the sensor in a given amount of time (shutter speed).

Aperture priority at f/5.6Aperture Priority on Top of Camera

Setting aperture priority on LCD screenAperture Priority on Camera LCD

The aperture can be adjusted on your camera to make different sizes of lens openings and the shutter speed or the ISO can be adjusted at the same time so that the overall exposure does not change and you still get a well-exposed photo.

Canon Aperture Priority

Just like other modern DSLR and mirrorless cameras, Canon has both manual and automatic camera settings that controls the size of the lens opening. Aperture mode is one setting I use more than any other-more on that in a minute!

Whether it's called Canon aperture mode, aperture priority mode, or simply aperture priority, it's an auto-exposure (AE) setting where you set the f/stop number and the camera will select the right shutter speed to get a properly exposed photograph.

It's not a fully automatic setting where the camera does everything for you. Think of it as a semi-automatic setting where both you and the camera are involved.

Canon aperture mode is an automatic exposure mode where you set the aperture manually and the camera automatically determines the best shutter speed to use to give you a good exposure. Aperture priority is the best setting to use when you want to control what's in and not in focus in your photo.

What does aperture mode do? In addition to controlling the amount of light coming through the lens, it also gives you control of the range of things that will be in focus (depth of field) in your photo. On some cameras it's designated with a capitol A. On your Canon camera it's a capitol A and a small v like this Av.

When You Should Use Aperture Mode

There are certain situations where using aperture mode makes perfect sense and other times when you'll want to avoid using it. The three most common photography situations where aperture mode is preferred are when you're shooting portraits, landscapes, and macro photography.

1. Use Aperture Mode For PORTRAITS

Aperture priority portraitF/stop set to f/3.5.

Use aperture especially with portraits of individuals (or an expecting couple), where you want your subjects to be in sharp focus and your background to be pleasantly out of focus.

You can use aperture mode and a low f/stop to blur the background. Notice this maternity portrait.

These parents-to-be were positioned so that their eyes are the same distance from the camera.

Using aperture priority mode, a telephoto lens, an f/stop of f/3.5 and focusing accurately on their eyes insures they'll be sharp and the background will blur nicely. 

Aperture mode is also a good fit for using when you're photographing a larger group, but for the opposite reason. You want everyone to be in sharp focus.

Small aperture group photoSmaller aperture to get everybody in focus.

If you're photographing a large group of people and some are close and some are more distant from the camera, you need to "stop down" to a smaller lens opening to increase that depth of field so that all of your subjects are in sharp focus.

2. Aperture Priority For LANDSCAPES

Many landscape photographs include objects that are close to the camera as well as far away that you want to be in sharp focus. Set your aperture to a small opening, typically f/16 or smaller, and everything in your landscape photo will be in sharp focus. See the example below.

Acadia landscape exampleAperture was set to f/13 to have everything in focus.
16mm wide angle lens.

Including near and far objects in a landscape photograph creates a visual pathway for your eye to travel. I wanted everything to be in sharp focus in the photo above. The super wide angle lens creates a strong perspective.

There are also other situations in landscape photography where you want to visually separate your subject from either the foreground, background or both by limiting the sharp focus area to just your main subject.

See the example below of what happens when you use a large aperture for photographing a close-by subject with a distant background.

Controlled depth of field exampleI used a large aperture to blur the background

While doing some landscape photography at Yosemite, I took a different approach at photographing the often photographed El Capitan. I decided to make it the background and put the focus on the yellow flowers contrasting with the beautiful blue sky. I used aperture priority and a large aperture.

For an additional popular setting for shooting landscapes see the post on Canon Picture Styles.

3. MACRO PHOTOGRAPHY And Aperture Control

When shooting macro photography the depth of field is extremely limited. Sometimes you may want that effect for creative purposes. In other situations you may want to "stop down" all the way to the smallest possible aperture (largest f/stop number) to get as much depth of field as possible.

Lily flower at f/18Lily close-up at f/18 aperture

In the photo above I wanted to get the entire pistil (center part) of the flower in focus, so I used aperture priority with the aperture set to f/18.

When shooting macro photographs it's a good idea to use aperture priority and take several different f/stop setting versions of your composition and look to see the different effect you get with each different aperture. You'll get a nice variety of background and foreground blurring. 

When Not To Use Aperture Mode

There are times when using shutter priority or manual mode make more sense than keeping your Canon camera set to aperture priority mode. These include situations where the length of the expoure is the most important setting to control


Aperture priority is generally not used when you want to use a shutter speed that is fast enough to freeze the action. Each specific type of sport or speed of the action has a corresponding shutter speed need to eliminate blur from motion.

Generally for sports, action, and rapidly moving wildlife (including birds in flight) you'll want to set your camera to shutter priority mode and set the camera at a specific speed. For recommended speeds see the article on shutter mode.

Of course, when you want the fastest possible shutter speed and the conditions are not the brightest, you can open your aperture to its maximum widest aperture to maximize the shutter speed under the lighting conditions you're presented with. 


When you're shooting indoor photos with flash as the main light source aperture priority is not a good setting to use. Shooting outside photos when it's dark is also not a good time to use aperture mode.

Manual exposure is the better choice for nighttime photos and you're usually using a tripod becasue of the longer shutter speeds required.

25 second exposure at f/4I shot this photo of the Big Dipper at f/4 for 25 seconds.


Don't use aperture priority when you're shooting long exposures for creative effects. You'll want to use either shutter priority or manual mode. In these shooting situations you want to control the exact shutter speed for the specific effect you're going for.

For instance, I shoot waterfall exposure for between 1 and 10 seconds depending on the amount and flow rate of the cascading water in my composition. You have to use "bulb" mode when star trails where exposure can be several minutes or more long. Aperture priority has a maximum shutter speed of 30 seconds.

How To Change Aperture On Your Canon

In order to change your aperture setting on your Canon camera you need to know where it is. Then it's simply a matter of rotating a dial or a wheel, or touching the right spot on the LCD panel on the back of your Canon.

Aperture Q&A

Do professional photographers use aperture priority mode?

Yes, aperture mode is a favorite camera setting for pro shooters, especially portrait photographers and landscape photographers

Is aperture priority mode a good setting for beginners?

Aperture mode is great for beginners who want to learn how to use focus to their advantage. Photographing friends and family is one of the most enjoyable subjects to start with and using aperture priority with a large lens opening is good for putting the emphasis on the people and not the background.

What is the main disadvantage of using aperture?

When you stop down to a very small aperture you're cutting down the amount of light that can come through the lens. You may get motion blur from the resulting slow shutter speed. Not all, but some lenses have poor image quality at their widest open settings.

To combat the motion blur you could raise the ISO, use a tripod for stationary subjects, or add flash to your lighting.

Does aperture affect quality?

Yes, the lens aperture you choose to use can have an effect on image quality. All other factors being equal, the best image quality for most lenses is usually attained when a lens is stopped down two or three f/stops from the maximum aperture.

This varies a lot from one lens to the next, but generally speaking prime lenses and professional lenses have less image quality degradation at the highest and lowest f/stops than consumer grade lenses with zooming.

Canon Aperture Video

Canon produced this short, but helpful video on aperture. It starts right away with the goo information and avoids the fluff in the beginning. Enjoy!

I hope this post was helpful in explaining why aperture is so important and when you should use aperture priority as a setting. Keep your curiosity high and have a blast shooting your Canon.

Author Bruce Lovelace
Bruce Lovelace Signature

Bruce Lovelace is the publisher of Canon Camera Geek. Read more about him on the About Page. He also publishes how to articles and camera gear reviews at the Photography Tips website.

View some of Bruce's photos on Instagram  and Flickr  Join the tribe of followers on YouTube. Bruce also runs photo workshops and provides 1 on 1 digital photography coaching.

Canon Geek on Google My Business

You might like these

Recent Articles

  1. Canon T3i Accessories-The Must Have T3i Gadgets And The Like To Have

    Apr 02, 24 02:02 PM

    The Canon t3i-Canon 70D-same accessories
    Great accessories for your Rebel Camera? Here are some ideas for Canon T3i Accessories that will help you improve your photography with your Rebel camera

    Read More

  2. Power Up Your Photography-Top Alternatives to the Canon 270EX II Flash

    Apr 02, 24 12:13 PM

    270EX II Alternative
    Unleash Your Flash Potential: Better, Cheaper Options Than the Canon 270EX II. Exploring Powerful Canon 270EX II Alternatives

    Read More

  3. Canon EF 16-35mm f/4 vs f/2.8: Focal Face-Off! Which Wide-Angle Wins?

    Mar 26, 24 01:37 PM

    Canon EF 16-35mm f/4.0 IS Lens
    There are 3 modern versions but which Canon 16-35mm lens is best. Helpful side by side comparison of the specs that matter. Helpful Canon EF 16-35mm lens guide

    Read More

  4. Is The Canon 50mm f/1.4 Lens Any Good. First Impression and How to Use

    Mar 26, 24 09:45 AM

    Bruce and 50mm f/1.4 lens
    Canon's Nifty Fifty: Friend or Foe? A Photographer's First Impressions of the 50mm f/1.4 My review with sample images. Is the Canon 50mm f/1.4 Lens Any Good

    Read More

  5. Best PowerShot Accessories And Why They Are Essential For Beginners

    Mar 23, 24 12:22 PM

    Canon Powershot accessories header
    You've got your Canon Powershot camera, but now you need to know what are the best Powershot accessories to start with for beginners. Helpful guide.l

    Read More

This page may contain affiliate links that pay me a small commission. There is no cost to you. Review the affiliate statement at the very bottom of this page if you want more information.

Sign up for a monthly update

Enter Your E-mail Address
Enter Your First Name

Don't worry — your e-mail address is totally secure.
I promise to use it only to send you Canon Geek Newsletter.