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Av: Aperture Priority Mode

eos_m_mode_icon_av.jpg You wouldn’t know it from its name, but Av mode is one of the most useful and popular modes in the Creative zone. Av stands for Aperture Value, and like Time Value, it’s another term that you’ll seldom hear a photographer toss around. Av, 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.

When to Use Aperture Priority (Av) Mode

  • When shooting portraits or wildlife (Figure 4.7)
    Figure 4.7

    Figure 4.7. A fairly large aperture coupled with a long focal length created a very blurry background, so all the emphasis was left on the subject.

  • When shooting most landscape photography (Figure 4.8)
    Figure 4.8

    Figure 4.8. The smaller aperture setting brings sharpness to near and far objects.

  • When shooting macro, or close-up, photography (Figure 4.9)
    Figure 4.9

    Figure 4.9. Small apertures give more sharpness in macro images.

  • When shooting architectural photography, which often benefits from a large depth of field (Figure 4.10)
    Figure 4.10

    Figure 4.10. A wide-angle lens combined with a small aperture makes for a large depth of field.

Aperture Priority is probably my favorite shooting mode, 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.

Aperture Priority mode is 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 Tv 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 Av Mode

  1. Tap the Mode button on the LCD, choose Av, and tap the Return button (return-button.jpg).
  2. Select your ISO: Tap the ISO button in the lower-right corner of the screen, turn the Main dial or drag to the desired setting, and tap the Return button.
  3. 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 LCD.
  5. While the meter is activated, use your index finger to roll the Main 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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