Aperture and Shutter Priority modes

In D-Photo’s continued push to help beginners move away from shooting in Auto mode, we speak with Matt Nixon of Photo & Video International about getting creative with the Priority modes

In Issue No. 53 we looked at shuffling that mode dial off Auto mode and starting to come to grips with exposure basics in Program mode. Now we’re going to get a little braver and explore Aperture Priority (often denoted as A or Av, for aperture value, on the mode dial) and Shutter Priority (S or Tv, for time value).

Why use Priority modes?

Most modern DSLR cameras will do a pretty decent job of exposing a shot when set in Auto mode, but by just pointing and shooting you’re not learning much as a photographer, and you’re sacrificing most of your control. As Matt Nixon from Christchurch’s Photo & Video explains, if you really want to get creative with your camera you need to move beyond Auto.

“Auto mode tends towards the middle ground, offering a safe but often uninteresting take on a scene,” he explains. “It’s perfect for that hurried moment when you just need something that will be usable, but not great for creating a more memorable and distinctive image.”

In order to ditch that automatic safety net, you must first grapple with the basic elements of exposure. As we saw in Issue No. 53, the semi-automatic Program mode is an ideal way to introduce yourself to aperture, shutter speed and ISO, and their effect on exposure. Aperture and Shutter Priority modes do much the same, while giving you a greater degree of control.

Aperture Priority

As you’ll remember from Issue No.53, the aperture is the hole through which light gets to your camera’s sensor. In Aperture Priority mode you select how big or small you want that opening to be by adjusting your camera’s command dial — the camera will automatically select an appropriate shutter speed to correctly expose the shot.

“This mode is great for any situation where you want either less or more depth of field than the middle ground Auto mode would tend to provide,” explains Nixon.

A large aperture (represented by a lower f-stop value) will result in a shallow depth of field which lets keep your subject in focus with the background blurred.

“Portraiture is a classic example where you are able to isolate the subject from the background and focus the viewers’ attention on your subject,” says Nixon.

Small aperture

Large aperture

It can also be useful in low light situations, as a larger aperture lets more light into your camera.

If you want to keep as much of your image in focus as possible then a smaller aperture (represented by a higher f-stop value) will give you a greater depth of field. This is often used for things like landscape shots.

“The thing to watch out for here is the lack of light entering the camera through what is now essentially a very small hole,” advises Nixon.

If you select a small aperture the camera will be forced to choose a slower shutter speed to expose the shot correctly. If the shutter speed gets too low you may end up with shaky images if hand-holding the camera. A tripod is an invaluable investment if you plan on shooting with a small aperture a lot.

Shutter Priority 

As you might assume, Shutter Priority mode gives you control over the flip side of the exposure equation. You select the shutter speed with your command dial and the camera automatically selects an appropriate aperture value.

“This is great for situations where you want to either introduce or limit motion blur,” Nixon advises.

If your aim is to represent motion in your image by introducing motion blur, then selecting a slower shutter speed is the way to go. As it takes the shutter longer to close, instead of freezing a subject’s motion the image will record it as more of a blur.

“Classic examples include water flowing through a landscape scene where the water is blurred to the point of looking soft and ethereal, or a cityscape where passing cars and people appear ghostly.”

Low shutter speed

High shutter speed

Just be sure not to introduce your own, unintended blur if the shutter speed gets too slow. “You could give up caffeine, but a tripod would be more socially acceptable,” Nixon helpfully suggests. 

On the other hand, if you’re tackling a fast-moving subject and want a sharp image in the frame, you’re going to need a high shutter speed. 

“Prime examples include sports and wildlife photography where having a fast shutter speed allows you to freeze action to a moment in time,” says Nixon.

Keep in mind if you set a fast shutter speed the camera is going to have to compensate with a larger aperture, reducing the depth of field and blurring your background.

Put it to practice

To really master your camera you need a solid grasp on all elements of exposure, and the Priority modes are a great way to experience the effects of shutter speed and aperture variation in action.

“A good way of getting to grips with the different modes is to go out and take the same images, but at either end of the scale,” Nixon explains. “For example, a portrait taken wide open followed by the same image shot stopped down to your lens’s minimum aperture. Doing this will give you real world insight into the effects that changing settings can have.”

Be sure not to get too reliant on one mode though, when we move on to Manual control next issue you’ll no longer have the camera’s semi-automatic help to rely on.