If you remember your exposure triangle, you know that the aperture is one of the fundamental camera settings determining your image quality and feel.
Aperture settings affect depth of field, rendering distances, and foreground and background separation in different ways.
Toying with aperture, especially on fast lenses, can be exciting and fun. But trying to wrap your head around the finer details of how the aperture interacts with other exposure settings can also be too complex for its own good.
When you find manual mode overwhelming, that’s when you should start considering the “A” position on your mode dial. That’s aperture priority mode, and today’s guide is going to revolve all around it. We will examine what aperture priority is, how it works, and how to use it for great, successful images.
Let’s get right to it!
How Shutter Speed and Aperture Determine Great Images
Both your aperture value as well as the shutter speed equally determine exposure. A small aperture decreases the amount of light entering the sensor. A fast shutter speed achieves the exact same. Conversely, you can compensate for an underexposed scene with either a wide aperture or a faster shutter speed.
The point where the aperture becomes more interesting for many photographers is in its ability to control depth of field. You can use shutter speed settings to selectively create blurry images or snap-freeze moving subjects.
Meanwhile, the aperture controls the separation between foreground and background elements as well as the depth of field.
This is especially important for portrait photography, but not only. A wide variety of genres, from macro photography to landscape photography, rely heavily on aperture control for image quality.
Generally speaking, any discipline where the element of motion blur is of little relevance will benefit more from careful use of aperture settings rather than shutter speed.
How Aperture Priority Makes Life Easier
That is exactly where aperture priority auto exposure comes in. Aperture priority compensates for exposure by automatically adjusting shutter speed based on your other camera settings. At the same time, it allows precise control over your lens diaphragm, just like in manual mode.
In plain English: aperture priority allows you to focus on composition and exposure purely by f-numbers while your camera takes care of the less important shutter speeds.
Go to your maximum aperture for that smooth bokeh effect, and the camera selects a faster shutter speed in response. At a narrow aperture, the shutter speed decreases automatically to likewise balance out your exposure.
Sounds great, doesn’t it?
How to Use Aperture Priority
On pretty much all modern cameras, aperture priority mode is found on the “A” position on your mode dial. On Canon cameras, the label is usually “Av mode” – same thing.
You don’t need to do anything special to activate aperture priority. Just slide the dial to the right position, focus, and take the shot!
Aperture priority was the first form of auto exposure that became available on consumer cameras in the 70s and 80s. That means it’s a well-established technology that doesn’t require any special lenses or fancy camera bodies in order to work.
An Intro to Exposure Compensation
However, that doesn’t mean that it takes no skill or precise control in order to get good results from Av mode. Plenty of beginners make the mistake of simply engaging the mode button in the A position and leaving it there, expecting the camera to do the rest.
Sure, that can work – but you’re missing out on one of the most powerful features of semi-automatic exposure. That feature is exposure compensation, which allows you to manually adjust the desired value of exposure.
In a sense, it’s an override to the shutter speed value the camera chooses for you. In that sense, it leaves you full control even in an “automatic” shooting mode.
Exactly how to use EV compensation depends a lot on your photographic scene in question. Compensation works via your camera’s built-in light meter, so metering modes will change how it affects your image quality.
For example, in a scene featuring human subjects where the sun is facing you, you can select a metering zone around your main subject and use exposure compensation to prevent blowing out the sky.
The specific aperture value might not be so important in this case. But as compensation does not apply in manual mode, choosing Av mode can nonetheless make your workflow a bit easier.
When Is Aperture Priority The Ideal Shooting Mode?
Gone are the days when the only choice you had was either to go full manual mode or aperture priority. Nowadays, most digital cameras come with a long list of shooting modes and exposure settings, including shutter priority mode and program mode.
With that in mind, how do you know which is best?
Let’s go over a few common scenarios many professional photographers face and see which cases are optimal for aperture priority.
Action photography With Shutter Priority
From photographing sports events for the local press to documenting a family vacation, most of us deal with some kind of action photography fairly frequently.
When your subjects are quick on the move, it makes sense to switch over from Av mode to shutter priority mode. This allows you to control motion blur in your images directly while the camera sets the aperture for you.
When you dial in a slow shutter speed to create a higher sense of motion, a small aperture value will automatically be selected. Conversely, snap-freezing your subject’s motion with a fast shutter speed will invoke a wide aperture on your camera lens.
Shooting Sports in Aperture Priority Mode
The above might make it sound like there’s a hard and fast rule: with moving subjects, always prefer direct control over shutter speed. However, that is not necessarily always the case.
In some fields, like photographing sports, plenty of pro photographers prefer Av mode for certain circumstances. For example, when you are shooting with a large telephoto or super-telephoto lens, the depth of field, even at moderate aperture settings, might be very thin.
In order to avoid rendering the subject out of focus at a crucial moment, some sports and action photographers like to switch to aperture priority.
That allows them to manually set small apertures, which has a twofold benefit. It both makes rapid focus much easier and lowers the risk of losing the subject in the background.
The appropriate shutter speed can then be determined with EV compensation or even in full manual mode. You can also intelligently set manual ISO to force your shutter speeds into the desired range in aperture priority mode. More on that technique in a bit!
Av Mode in Portraiture
Shooting portraits is one of the oldest and still most popular forms of photographic expression.
Because subjects in portraiture will usually remain fixed in place, there is little reason for using shutter priority mode. Even manual mode is hardly essential, in fact!
Your desired aperture has by far the greatest effect on the results of any portrait photograph compared to shutter speed or other settings.
Many portraitists prefer a shallow depth of field to isolate their subject from the background strongly. This is remarkably easy to achieve using Av mode. Just dial in a wider aperture, and the camera selects the appropriate shutter speed for you!
By combining aperture priority with exposure compensation, exposure control over the entire scene is fairly straightforward.
The Difference Between Aperture Priority Mode and Manual Mode
In cases such as in the above example of portraiture, it can often be hard to decide between aperture priority and manual mode. How much is the added control over shutter speed worth it in real-life photography?
The answer will depend as much on your personal shooting style as on your camera gear. Environmental factors do of course also come into play.
For example, when shooting portraits, as we described above, using a fast lens on a stabilized camera with a large sensor, manual shutter speed control is not essential. With such great depth of field at your disposal, you will be able to neatly define exposure using solely the lens diaphragm. You can let your camera control the correct exposure by means of shutter speed automatically to minimize fiddling.
However, in situations where you will not have as much control over the depth of field, manually setting shutter speed can actually be really helpful. Instead of relying on EV compensation, you can take complete control yourself and use the shutter to balance out ambient light conditions.
Even in cases where you aren’t particularly restricted, full control may still be desirable.
In landscape photography, for instance, careful use of shutter speed and aperture to handle both exposure and depth of field is basically essential. You could as well use aperture priority mode and even out a smaller aperture with more EV compensation.
But by switching to manual, you get the exact same advantages with even finer control right at your fingertips.
Comparing Aperture Priority And Shutter Priority Mode
When to use either aperture priority mode or shutter priority is once again a question that depends a lot on your shooting environment and other factors.
Generally speaking, most professional photographers will pick aperture priority mode over a manual shutter speed control for circumstances where speed is less of a concern than pinpoint focus and depth of field.
Conversely, in action photography and other high-speed environments, shutter speed becomes more of a vital concern. Instead of using the lens aperture to cast less or more light onto the sensor, the same can be achieved purely by the shutter.
One added benefit is that different shutter speeds allow you direct control over motion. That control allows you to create pin-sharp or blurry images on demand.
Another advantage comes into play in flash photography. Because most digital cameras have a certain minimum shutter speed for flash synchronization, manual control can become essential.
In combination with flash, you can use shutter priority mode to both compensate for low light as well as determine proper exposure. A slow shutter speed makes for a brighter exposure in the background, whereas a faster speed tones down highlights and sharpens moving subjects.
Aperture Priority Compared with Program Mode
There is more to the mode dial on your camera than just Av and S modes. Almost all consumer-grade digital photography gear nowadays also features a third automatic exposure mode labeled P.
Program mode takes the best of both words – literally. It uses an advanced metering readout to calculate both aperture and shutter speed based on lighting conditions. That leaves you only with focus, focal length, and ISO to manually play with.
Program mode is very useful for when you want to waste as little time as possible setting up your exposure whilst still getting usable results. In the right hands, program automation can be ridiculously fast, especially when coupled with burst shooting.
However, the nature of the camera selecting all essential exposure settings on your behalf does mean that the Program mode lacks a certain degree of flexibility. You can use EV compensation to nudge the meter’s preferred values a little.
But what if you would like a completely different exposure than what program automation suggests, a narrow aperture and low shutter speed instead of the reverse, for example? While possible, it can be unnecessarily tricky to dial that in without switching back to a different mode.
Aperture Priority and ISO – The Great Debate
So far, we have mostly been looking at the relative values of aperture priority mode and shutter speed priority. Program automation, as a combination of the two, is more of a wild card suited for specific circumstances, while full manual mode is great for those who prefer full control.
However, there is one more exposure element that can be essential to numerous shooting profiles. Like its two siblings, it can function either manually or automatically.
Of course, I am referring to ISO. Your sensor sensitivity affects your images a great deal by directly altering how much light it takes to create a certain exposure. This always comes with advantages and certain trade-offs depending on the setting.
At a low ISO of 100, you might not be able to shoot fast-paced street scenes at a low aperture setting. On the other hand, portraits will be crisp, noise free, and easy to shoot with a wide aperture.
A high ISO of 1600, ideal for low light, will be so high that you won’t be able to use your maximum aperture during the day without severely overexposing or choosing an extreme shutter speed.
This opens up a decisive question. Is it wiser to set your ISO yourself or leave it to the camera settings to figure it out automatically? Let’s take a look and decide.
Advantages of Setting ISO Manually
Individually setting your ISO – whether for each picture, for each day of shooting, or anywhere in between – can minimize guesswork in many kinds of photography.
Let’s use one of our previous examples, shooting portraits. In the context of portraiture, you would probably prefer a shallow depth of field combined with a medium telephoto lens of high focal length. A low-noise image, with plenty of detail and sharpness, is also desirable.
This means that most of your daylight shots will likely feature a wide aperture with a fast shutter speed. Setting your ISO to something low, like 100 or 200, is a reliable way of ensuring that your exposure will stay in that ideal range.
This applies even when you use aperture priority mode or other automatic aperture controls apart from ISO.
When to Dial in Auto ISO
Conversely, auto ISO can be very nice to have when your environment is particularly challenging and unpredictable.
Photojournalists make particularly liberal use of auto ISO for just that reason. When you don’t know in what kind of lighting and from what angle the next opportunity for a picture will come, leaving auto ISO engaged gives you one less item on the camera mode dial to worry about.
Auto ISO will intelligently compensate for your other settings and the ambient light to figure out the appropriate exposure value. This works even in full manual mode – a handy way of giving a slight element of automatic refinement to manual control.
Using Aperture Priority to Your Benefit
As you have seen today, aperture priority mode lets you take control of your camera’s vast capabilities in a unique way. It can be highly useful in some circumstances, less so in others.
What matters most is not trying to use aperture priority wherever you can and treating it as some kind of “easy mode button” to take great images with little effort.
Rather, utilizing Av mode in accordance with its strengths is the hallmark of a skilled photographer.
Now, go out and apply what you have learned! Only by using aperture priority in real-life situations can you fully develop an intuitive understanding of its pros and cons. Good luck!