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Aperture Priority Mode (A)

You wouldn’t know it from its name, but Aperture Priority mode is one of the most useful and popular modes in DSLR photography. Aperture Priority is one of my personal favorite modes, and I believe that it will quickly become one of yours as well. Aperture Priority is also deemed a semi-automatic mode because it allows you to once again control one factor of exposure while the camera adjusts for another.

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 element in how you direct attention to what is important in your image. It is the controlling factor when determining how much of your image is sharp. 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 your emphasis is on keeping the entire scene sharply focused, such as with a landscape scene, then using a small aperture will render the greatest depth of field possible.

When to use Aperture Priority Mode

  • When shooting portraits or wildlife (Figure 4.6)
    Figure 4.6

    Figure 4.6. A large aperture and long lens helped to separate this little guy from the rocks in the background.

  • When shooting most landscape photography (Figure 4.7)
    Figure 4.7

    Figure 4.7. Using smaller apertures ensures that you will get sharp landscape shots.

  • When shooting macro, or close-up, photography (Figure 4.8)
    Figure 4.8

    Figure 4.8. The large aperture helps focus attention on the water drops on the flower.

  • When shooting architectural photography, which often benefits from a large depth of field (Figure 4.9)
    Figure 4.9

    Figure 4.9. A large depth of field ensures sharpness from near to far.

So we have established that Aperture Priority (A) mode is highly useful in controlling the depth of field in your image. But 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, or f-stop, the less light you need to achieve an acceptably sharp image. You will recall that, when in Shutter Priority mode, there is a limit at which you can hand-hold your camera without introducing movement or hand shake, which causes blurriness in the final picture. If your lens has a larger aperture, then 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 Aperture Priority Mode

  1. Turn your camera on. Press and hold the Mode button while turning the Main Command dial until you see an A in the control panel.
  2. Set your ISO by pressing the ISO button; select the appropriate setting by looking at the ISO readout on the control panel or by pressing the Info button on the back of the camera and looking at the info display on the rear LCD monitor (Figure 4.10).
    Figure 4.10

    Figure 4.10. The info screen in Aperture Priority mode.

  3. Once your ISO is set, point the camera at your subject and then activate the camera meter by depressing the shutter button halfway.
  4. View the exposure information in the bottom area of the viewfinder or in the control panel.
  5. While the meter is activated, use your index finger to roll the Sub-command 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).
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