How to Start Using Aperture Priority and How It Will Change Your Photography

If you’ve been learning photography and have started to take your first steps outside of your camera’s program mode, aperture priority can help you get to grips with your camera and develop your knowledge. This camera mode can make shooting easier and open up more creative possibilities.

Your camera's aperture has a large bearing on how much of a scene will be in focus. Landscape photographers often use a small aperture to get as much in focus as possible; by contrast, portrait photographers using natural light will often use a large aperture to make a subject sharp but leave everything else out of focus.

How Aperture Priority Compares to Program Mode

While program mode will prompt the camera to make the vast majority of decisions for you, aperture priority (typically on your camera’s dial as “A” or “Av”) allows you to set the aperture and then let the camera decide the exposure by changing the shutter speed.

For this tutorial, let’s assume that we’re shooting people using a DSLR or mirrorless camera, that we're using a 50mm lens, and that want to have our subject sharp but our background as blurry as possible. To achieve this pleasing, cinematic effect, a large aperture will create a shallow depth of field, and even the cheapest 50mm prime lens offers a wide aperture of f/1.8. If your variable aperture kit lens feels like a limitation and you want to see how f/1.8 compares to, say, f/5.6, it’s worth splashing out a tiny amount on a nifty fifty, such as this one.  (Keep in mind that accurate focusing is very important, as the margin for error is much smaller.)

Getting Started in Aperture Priority

When you start shooting in aperture priority, it’s a good idea to adjust your aperture using the dial under the thumb of your right hand rather than the one under your forefinger. This is a habit that you will appreciate if and when you start shooting in manual mode. (If your camera only has one dial, don’t worry.) 

To choose your widest available aperture, scroll this wheel to the left until you get the lowest available number. (Note that if you are using a kit lens, the widest available aperture may vary depending on how far you are zoomed in. This is often a limitation of lower-end lenses: as you zoom in, the largest available aperture becomes slightly smaller.)

The next step is to tell your camera to choose the ISO automatically, a setting that typically has to be applied by scrolling through the available ISO numbers and past the camera’s lowest ISO (for example, 100 or 50) to “AUTO ISO.”

Set a Minimum Shutter Speed

In aperture priority mode, you probably want to avoid having the camera automatically choose a shutter speed that is so low that your images are blurry because you cannot hold the camera still enough, and setting a minimum shutter speed is one solution. You may have to use a search engine to find out if your camera has this option and then dig through the menus in order to set it. (Unfortunately, many entry level cameras don’t have this option, but don’t worry too much. Skip to the next section and keep in mind that your images might get blurry if you’re shooting in very low light.)

Finding the right part of the menu can be tricky. For Canon, it’s often in “ISO Speed Settings,” while for Sony, have a look for “ISO AUTO Min. SS.” For Nikon, I believe it’s found under “ISO Sensitivity Settings.” If you’re using a standard kit lens or a 50mm prime, I suggest setting this to 1/250th of a second. With a 50mm lens, 1/60th is just about fast enough to avoid camera shake when shooting handheld, but you typically want a shutter speed that is a little faster as anything that is moving in your frame can easily become blurred.

On my Sony a7 III, I have this minimum shutter setting assigned to one of my customizable buttons allowing me to change it on the fly rather than churning through Sony’s menu system. For natural light portraits, 1/125th is sufficient. For candid shots of people. you probably want something a little quicker. For my climbing photography, I usually choose 1/250th or 1/500th. For my parkour photography, typically I’m shooting at 1/1000th or faster.

Start Shooting

With your aperture at its widest, your ISO set to auto, and your minimum shutter speed set to 1/250th, you’re ready to start shooting. If you head out in bright sunlight and begin taking photographs, there’s a good chance that your camera will choose its lowest possible ISO and your camera’s fastest shutter speed (for example, 1/4000th or 1/8000th of a second). When you shoot a much darker scene (for example, indoors), the camera will drop the shutter speed to 1/250th. If it’s still too dark, rather than dropping the shutter speed any lower, the camera will increase the ISO.

The big advantage of this set up is that your camera will give you an image with the least noise (i.e., the lowest possible ISO) without introducing camera shake (i.e., it won’t choose a shutter speed that’s too slow). If you’re out shooting candid portraits of your friends and family, this is a perfect setup and is also the choice of many professional wedding photographers.

Perfecting Your Technique With Exposure Compensation

If you’re shooting up at a subject who's standing with a bright sky behind them, there’s a very good chance that your image will be underexposed, as the camera will try to account for the large amount of light entering the lens. If you’ve ever shot a picture of someone and their face is a shadow, but you have a perfectly exposed sky, this is the reason. At this point, you want to have a bit more control over the choices that your camera is making automatically.

One option is to switch from aperture priority to manual mode and select either a higher ISO or a slower shutter speed to create a brighter exposure. However, we can force the camera to choose the brighter exposure without leaving aperture priority mode simply by using exposure compensation. Many higher-end cameras have a dedicated dial. If you turn it to the right, the camera automatically sets an exposure that is brighter; turn it to the left, and it gets darker. Changing the exposure compensation on lower-end cameras is usually possible, but typically requires holding a "+/-" button while turning a dial.

One of the disadvantages of using exposure compensation is that forgetting to reset it to zero afterwards can be quite frustrating.

Take Total Control With Auto Exposure Lock

If I’m walking with friends through the forest where I live or shooting candidly outdoors with clouds occasionally passing in front of the sun, letting the camera sort out my exposure for me allows me to shoot more quickly. I know I want the widest aperture, and having my camera make the rest of the decisions for me makes shooting effortless, allowing me to switch seamlessly between climbing and photographing without much effort. However, there are occasions when the camera’s decision-making is not ideal.

An example might be capturing someone as they climb higher up a rock. As they ascend, there’s a good chance that there will be more sky in the background and consequently, more light entering the lens. If I’m not careful, my subject can become quickly underexposed. Another example might be shooting a series of portraits and shifting from a centered subject to one where the subject is in the corner of the frame. With a backlit subject, this can suddenly mean that the camera detects a lot more light entering the lens and underexposes again.

One option is to tweak my exposure compensation dial as I take each shot, but reframing might suddenly mean that my frame is massively overexposed. Instead, I can find my perfect exposure and tell my camera to lock my settings using the auto exposure lock function. The location of this button varies between manufacturers, and on my Sony, I’ve assigned it to a customizable button so that I can simply toggle it on and off rather than having it reset between shots. When locked, I can still use my exposure compensation dial to make small adjustments.

In Summary

If you want to start getting to grips with aperture priority, here's a quick summary of my suggested route:

• Choose your widest available aperture, ideally something like f/1.8 on an affordable 50mm prime lens.
• Set your ISO to auto and, if your camera has the option, set your minimum shutter speed to 1/250th of a second.
• If your image is underexposed, try setting your exposure compensation to +1. If overexposed, try -1.
• To give yourself even more control, find out how to toggle your camera's exposure lock on and off.

As my photography has evolved, so has the way that I operate my camera. The methods described above have made casual, candid photography much easier. By contrast, as soon as I’m choreographing action, I switch to manual mode, as I prefer to know what my camera is doing all the time.

Other photographers will have their preferred working methods, and each will have its own advantages and disadvantages, often largely determined by what you’re shooting. Take the tutorial above as one method of photographing and see how it works for you. If you have any questions, be sure to leave them below.

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