A: Aperture Priority Mode
You wouldn’t know it from its name, but A mode is one of the most useful and popular of the advanced modes. It is one of my favorites, and I believe that it will quickly become one of yours as well. A mode, more commonly referred to as Aperture Priority mode, is also deemed a semiautomatic mode because it allows you to once again control one factor of exposure while the camera adjusts for the other.
Why, you may ask, is this one of my favorite modes? It’s because the aperture of your lens dictates depth of field. Depth of field, along with composition, is a major factor in how you direct attention to what is important in your image. It is the factor that controls how much of your image is in focus. If you want to isolate a subject from the background, such as when shooting a portrait, you can use a large aperture to keep the focus on your subject and make both the foreground and background blurry. If you want to keep the entire scene sharply focused, such as with a landscape, then using a small aperture will render the greatest possible depth of field.
When to use Aperture Priority (A) mode
When shooting portraits or wildlife (Figure 4.6)
Figure 4.6 A fairly large aperture coupled with a longer focal length created a very blurry background, so all the emphasis was left on the subject.
ISO 200 • 1/80 sec. • f/2.2 • 55mm lens
When shooting architectural photography, which often benefits from a large depth of field (Figure 4.7)
Figure 4.7 A wide-angle lens combined with a small aperture makes for a large depth of field.
ISO 100 • 1/250 sec. • f/13 • 24–70mm lens at 40mm
When shooting macro, or close-up, photography (Figure 4.8)
Figure 4.8 Small apertures give more sharpness in macro detail shots.
ISO 100 • 1/20 sec. • f/8 • 100mm lens
When shooting landscape photography (Figure 4.9)
Figure 4.9 The smaller aperture setting brings sharpness to near and far objects.
ISO 100 • 1/40 sec. • f/14 • 16–35mm lens at 20mm
We have established that Aperture Priority (A) mode is highly useful in controlling the depth of field in your image. It’s also pivotal in determining the limits of available light that you can shoot in. Different lenses have different maximum apertures. The larger the maximum aperture, the less light you need in order to achieve a properly exposed image. You will recall that, when in S mode, there is a limit at which you can handhold your camera without introducing movement or hand shake, which causes blurriness in the final picture. If your lens has a larger aperture, you can let in more light all at once, which means that you can use faster shutter speeds. This is why lenses with large maximum apertures, such as f/1.4, are called “fast” lenses.
On the other hand, bright scenes require the use of a small aperture (such as f/16 or f/22), especially if you want to use a slower shutter speed. That small opening reduces the amount of incoming light, and this reduction of light requires that the shutter stay open longer.
Setting up and shooting in A mode
- Turn your camera on and then turn the Mode dial to align the A with the indicator line.
- Select your ISO by pressing the right side of the Control wheel (next to where it reads ISO), rotating the Control wheel to the desired setting, and pressing the middle of the wheel to select (the ISO selection will appear in the electronic viewfinder and the rear LCD panel).
- Point the camera at your subject, and then activate the camera meter by depressing the shutter button halfway.
- View the exposure information in the electronic viewfinder or on the rear display.
- While the meter is activated, use your thumb to roll the Control dial left and right to see the changed exposure values. Roll the dial to the right for a smaller aperture (higher f-stop number) and to the left for a larger aperture (smaller f-stop number).