Editor's note: This month only – you can buy two of my favorite ebooks, The Creative Photographer and Square, for just $7 each! Limited time only – click the links to learn more. Thanks for reading, Andrew
Aperture Priority mode is one of four exposure modes that give you full creative control over your camera (the others are Shutter Priority, Program Auto and Manual Mode).
What is full creative control? Let’s say you have a camera with fully automatic exposure modes (such as Landscape or Portrait). If you choose one of these modes, your camera decides what settings to use, such as aperture, shutter speed, ISO, white balance and color profile. Some cameras (for example, Canon EOS) even make you use the JPEG format without an option to switch to Raw.
These are all important settings. If you want to be a creative photographer and make beautiful photos, you need to take control of them.
That’s where Aperture Priority mode comes in.
How do I set Aperture Priority mode?
Most cameras have a Mode Dial with Aperture Priority marked on it. Set your Mode Dial to either A or Av (Aperture value) to activate Aperture Priority mode.
On some basic model cameras there is no Mode Dial and you have to activate Aperture Priority mode in the menu settings.
On Fujifilm X series cameras you can activate Aperture Priority by setting shutter speed to Auto and dialing in the required Aperture and ISO settings.
How do you use Aperture Priority mode?
There are two ways to use Aperture Priority mode.
In the first, you set the aperture and ISO, and the camera sets the shutter speed according to what its internal light meter says is the correct exposure. If this is wrong, you can override it using exposure compensation.
Learn more: Why Cameras Get Exposure Wrong
Learn more: Exposure Compensation or Manual Mode?
In the second, you set the aperture, and enable Auto ISO. Your camera sets both ISO and shutter speed according to its internal meter. Again, you can override the settings with exposure compensation.
Auto ISO may seem like a good idea, but in practice it’s more straightforward to set the ISO to a specific value. That way the camera can only change one exposure setting (shutter speed) which gives you more control.
When should I use Aperture Priority mode?
Aperture Priority mode suits the following subjects.
For most landscape photos you’ll want the entire scene to be in focus. That means using a small aperture, such as f8 or f11 (see below to see why you should avoid f22).
In landscape photography it’s conventional to use a wide-angle lens (to get more of the scene in), a low ISO (better image quality) and to shoot in low light (better quality of light equals better landscape photos).
The extra depth of field that wide-angle lenses give you helps create sharp images.
For example, I made this landscape using an 18-55mm kit lens set to 18mm on an APS-C camera. I set the aperture to f14 to make sure the entire scene was sharp.
Landscape photos and telephoto lenses
But you can use longer focal lengths to isolate interesting parts of the scene. If you’re shooting in low light (better light for landscape photography) and using a low ISO (better image quality) you’ll need to use a good quality tripod to keep your camera steady and avoid camera shake.
I made the photo below with a 56mm lens on an APS-C camera, with ISO 200, an aperture of f8 and a shutter speed of 1/4 second.
Landscape photos and slow shutter speeds
A secondary effect of using small apertures, low ISOs and working in low light is that the shutter speed required to give a good exposure is relatively long. For this reason landscape photographers tend to use tripods to keep the camera steady and avoid camera shake.
Longer shutter speeds are often a good thing in landscape photography, as they blur moving parts of the landscape, such as grass blowing in the wind, or water. The end result is a moodier, more atmospheric photo.
In the seascapes below slow shutter speeds blurred the motion of the water. This was a natural result of setting the aperture to f11 and ISO to 200 (the camera’s lowest setting).
Aperture and diffraction
You may be wondering why landscape photographers don’t use f22. The reason is that photos aren’t as sharp at small aperture settings such as f22 because of an optical effect called diffraction. You don’t need to know what causes diffraction (in simple terms it’s because light rays spread out as they pass through narrow apertures which softens the image slightly), but you do need to know it exists and how to avoid it.
• If you have a Micro Four-thirds or APS-C camera, then don’t use an aperture smaller than f11 unless you really need to.
• If you have a full-frame camera then don’t use an aperture smaller than f16.
Portrait photography is another area where photographers use aperture priority for creative effect.
If you have a prime lens, such as a 50mm or 85mm lens, then you can use the widest aperture settings to create portraits with very narrow depth of field. The idea is to focus on the model’s eyes and let the rest of the portrait go out of focus.
I made both these portraits with an 85mm lens on a full-frame camera and an aperture of f1.8.
It’s fun to play with wide aperture settings, but in practice you’ll find you may get better results at f2.8 or even f4. The aperture is still large enough to get plenty of background blur, and you’ll get more of the model’s face in focus.
For example, using an aperture of f4 with this portrait ensured that the model’s dreadlocks were in focus.
Environmental portraits and wide-angle lenses
Another approach to portrait photography is to use a normal or wide-angle lens with a smaller aperture so that more of the background is in focus.
To make this approach work you need to step back so that more of the model is in the frame. This prevents distortion caused by getting too close with a wide-angle lens.
It also means that you get to see more of the background in the photo. This approach is used by documentary photographers to tell a story about their subject.
You can do the same by making portraits where the background tells the viewer something about the model.
For example, these portraits have an interesting background that tells an interesting story about the blacksmith in the portrait. I used a normal lens and an aperture of f3.6 for each to make sure as much as possible was in focus.
Macro and close-up photography
Aperture isn’t the only factor that affects depth of field. Another major factor is lens to subject distance – the closer you get to your subject, the less depth of field there is.
This is critical in close-up and macro photography where depth of field is very small.
I made this photo using a 35mm lens (on an APS-C camera) fitted with an extension tube and set to f2.8. As you can see, very little of the flower is in focus.
Using high ISOs
As depth of field is so small you need to get used to using smaller apertures. You also need to get used to using higher ISO settings to indirectly control the shutter speed (when you raise the ISO the shutter speed gets faster).
This is important as you need a fast shutter speed to prevent blur caused by camera shake or subject movement (such as flowers moving in the wind).
Don’t be afraid of high ISOs – the image quality from modern cameras is excellent and it’s more important to get good depth of field and no camera shake than it is to use a low ISO.
I made both these close-up photos with ISO set to 3200. I didn’t have much choice as I was indoors and there wasn’t much light.
Street and travel photography
You can also use Aperture Priority mode when you are traveling or taking photos in the streets. One of the problems associated with this style of photography is cluttered backgrounds.
You often don’t have much control over the background, especially if you’re in a busy place. But you can blur busy backgrounds by using wide apertures, like in this photo.
Another technique is to use a wide aperture to push foreground objects out of focus, so they don’t become distractions.
You can also use wide apertures to blur the background of your photos with the aim of making them look more mysterious.
If you haven’t used Aperture Priority mode on your camera before then I hope this tutorial has inspired you to give it a try. Aperture is one of your camera’s important settings and good photographers know how to use it to get the results they want. Aperture Priority mode makes it easy.
Thanks for reading. You can get more great articles and tips about photography in my popular Mastering Photography email newsletter. Join today and I’ll send you 47 PhotoTips cards and my ebook Introducing Lightroom Classic . Over 30,000 photographers subscribe. Enter your email now and join us.